Surface treatment method for nickel-based metallic glasses to reduce nickel release

ABSTRACT

Surface treatment methods for Ni-based metallic glasses are provided that promote passivation and decrease the amount of Ni released when the Ni-based metallic glass is exposed to a saline containing environment.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional Patent Application No. 62/233,488, filed on Sep. 28, 2015, U.S. Provisional Patent Application No. 62/299,366, filed on Feb. 24, 2016 and U.S. Provisional Patent Application No. 62/364,063, filed on Jul. 19, 2016, entitled “SURFACE TREATMENT METHOD FOR NICKEL-BASED METALLIC GLASSES TO REDUCE NICKEL RELEASE,” which are incorporated herein by reference in their entirety.

FIELD

The disclosure is directed to Ni-based metallic glasses having passive layers that limit Ni leaching when the metallic glasses are exposed to a saline containing environment, and surface treatment methods for Ni-based metallic glasses to promote formation of such passive layers.

BACKGROUND

Human tissue contains approximately 0.1 ppm of Ni. Higher Ni release from materials exposed to biological environments, e.g. used as implants or placed in the mouth or in contact with the skin, may generate harmful allergic, toxic, or carcinogenic reactions. Alloys that are Ni-based (i.e. containing Ni at an atomic concentration of at least 50%) are therefore of particular concern, as the Ni release from such materials can be expected to be rather high. There is a need for a Ni-based metallic glass capable of resisting Ni leaching when exposed to a biological environment.

SUMMARY

The disclosure is directed to surface treatment methods for Ni-based metallic glasses to reduce the amount of Ni released when the Ni-based metallic glass is exposed to a saline containing environment.

In one embodiment, the disclosure is directed to a surface treatment method for a Ni-based metallic glass. At least a portion of a sample of a Ni-based metallic glass is immersed in a chemical treatment solution to produce a surface treated portion. The surface treated portion is removed from the chemical treatment solution to terminate the chemical surface treatment. The chemical treatment solution comprises at least one of an acid solution, a chromate solution, and a molybdate solution. The Ni ion release rate from the surface treated portion of the sample when immersed in a saline solution for one day is less than 80% of the Ni ion release rate from an as-cast Ni-based metallic glass sample having the same composition immersed in the same saline solution for the same period.

In another embodiment, the surface treatment method comprises at least two immersion steps.

In another embodiment, the surface treatment method comprises at least two immersion steps, wherein at least one step comprises immersion in a first chemical treatment solution comprising an acid and at least one other step comprising immersion in a second chemical treatment solution comprising a chromate solution. In such embodiments, each immersion step comprises immersing at least a portion of the Ni-based metallic glass in a chemical treatment solution to produce a surface treated portion. The surface treated portion then is removed from the chemical treatment solution. In some embodiments, the first chemical treatment solution is an acid solution while the second chemical treatment solution is a chromate solution.

In another embodiment, the second chemical treatment solution is a sodium dichromate solution.

In another embodiment, the sodium dichromate concentration in the sodium dichromate solution is between 5 and 200 g/L.

In another embodiment, the surface treatment method comprises at least two immersion steps, wherein at least one step comprises immersion in a first chemical treatment solution comprising an acid and at least one other step comprising immersion in a second chemical treatment solution comprising a molybdate solution. In such embodiments, each immersion step comprises immersing at least a portion of the Ni-based metallic glass in a chemical treatment solution to produce a surface treated portion. The surface treated portion is then removed from the chemical treatment solution. In some embodiments, the first chemical treatment solution is an acid solution while the second chemical treatment solution is a molybdate solution.

In another embodiment, the second chemical treatment solution is a disodium molybdate.

In another embodiment, the disodium molybdate concentration in the disodium molybdate solution is between 10 and 100 g/L.

In another embodiment, the duration of immersion is at least 1 minute.

In another embodiment, the duration of immersion is at least 10 minutes.

In another embodiment, the duration of immersion is at least 20 minutes.

In another embodiment, the duration of immersion is at least 30 minutes.

In another embodiment, the duration of immersion is at least 60 minutes.

In another embodiment, the temperature of the chemical treatment solution ranges between 10 and 80° C.

In another embodiment, the temperature of the chemical treatment solution ranges between 20 and 60° C.

In another embodiment, the temperature of the chemical treatment solution is in the range of 20 to 30° C.

In another embodiment, the temperature of the chemical treatment solution is in the range of 40 to 60° C.

In another embodiment, the first chemical treatment solution comprises a nitric acid solution.

In another embodiment, the nitric acid concentration in the nitric acid solution is between 5 and 60 vol. %.

In another embodiment, the nitric acid concentration in the nitric acid solution is between 20 and 45 vol. %.

In another embodiment, the nitric acid concentration in the nitric acid solution is between 15 and 30 vol. %.

In another embodiment, the nitric acid concentration in the nitric acid solution is between 20 and 25 vol. %.

In another embodiment, the disclosure is directed to a surface treatment method for a Ni-based metallic glass. At least a portion of a sample of a Ni-based metallic glass is immersed in an acid solution to promote chemical surface treatment. The sample is removed from the acid solution to terminate the chemical surface treatment. Afterwards, the Ni ion release rate from the treated portion of the sample when immersed in a saline solution for one day is less than 80% of the Ni ion release rate from an as-cast Ni-based metallic glass sample having the same composition immersed in the saline solution for one day.

In another embodiment, the Ni ion release rate from the treated portion of the sample when immersed in a saline solution for one day is less than 60% of the Ni ion release rate from an as-cast Ni-based metallic glass sample having the same composition immersed in the saline solution for the one day.

In another embodiment, the Ni ion release rate from the treated portion of the sample when immersed in a saline solution for one day is less than 50% of the Ni ion release rate from an as-cast Ni-based metallic glass sample having the same composition when immersed in the saline solution for the one day.

In another embodiment, the Ni ion release rate from the treated portion of the sample when immersed in a saline solution for one day is less than 40% of the Ni ion release rate from an as-cast Ni-based metallic glass sample having the same composition immersed in the saline solution for the one day.

In another embodiment, the Ni ion release rate from the treated portion of the sample when immersed in a saline solution for one day is less than 20% of the Ni ion release rate from an as-cast Ni-based metallic glass sample having the same composition immersed in the saline solution for the one day.

In another embodiment, the Ni ion release rate from the treated portion of the sample when immersed in a saline solution for 4 days reaches a steady state.

In another embodiment, the Ni ion release rate from the treated portion of the sample when immersed in a saline solution for 2 days reaches a steady state.

In another embodiment, the Ni ion release rate from the treated portion of the sample when immersed in a saline solution for one day reaches a steady state.

In another embodiment, the Ni ion release rate from the treated portion of the sample when immersed in a saline solution for 12 hours reaches a steady state.

In another embodiment, the Ni ion release rate from the treated portion of the sample when immersed in a perspiration solution is less than 0.88 μg/cm²/week.

In another embodiment, the Ni ion release rate from the treated portion of the sample when immersed in artificial perspiration is less than 0.88 μg/cm²/week.

In another embodiment, the Ni ion release rate from the treated portion of the sample when immersed in a perspiration solution is less than 0.5 μg/cm²/week.

In another embodiment, the Ni ion release rate from the treated portion of the sample when immersed in a perspiration solution is less than 0.1 μg/cm²/week.

In another embodiment, the Ni ion release rate from the treated portion of the sample when immersed in a perspiration solution is less than 0.05 μg/cm²/week.

In another embodiment, the Ni ion release rate from the treated portion of the sample when immersed in a perspiration solution is less than 0.01 μg/cm²/week.

In another embodiment, the mass of Ni ion released from the treated portion of the sample when immersed in a saline solution for one day is less than 35 μg.

In another embodiment, the mass of Ni ion released from the treated portion of the sample when immersed in a biological solution for one day is less than 35 μg.

In another embodiment, the mass of Ni ion released from the treated portion of the sample when immersed in blood or saliva for one day is less than 35 μg.

In another embodiment, the mass of Ni ion released from the treated portion of the sample when immersed in artificial blood or artificial saliva for one day is less than 35 μg.

In another embodiment, the duration of immersion in the chemical treatment solution is at least 1 minute.

In another embodiment, the duration of immersion in the chemical treatment solution is at least 10 minutes.

In another embodiment, the duration of immersion in the chemical treatment solution is at least 20 minutes.

In another embodiment, the duration of immersion in the chemical treatment solution is at least 30 minutes.

In another embodiment, the duration of immersion in the chemical treatment solution is at least 60 minutes.

In another embodiment, the temperature of the chemical treatment solution ranges between 10 and 80° C.

In another embodiment, the temperature of the chemical treatment solution ranges between 20 and 60° C.

In another embodiment, the temperature of the chemical treatment solution is in the range of 20 to 30° C.

In another embodiment, the temperature of the chemical treatment solution is in the range of 40 to 60° C.

In another embodiment, the duration of immersion in the acid solution is at least 1 minute.

In another embodiment, the duration of immersion in the acid solution is at least 10 minutes.

In another embodiment, the duration of immersion in the acid solution is at least 20 minutes.

In another embodiment, the duration of immersion in the acid solution is at least 30 minutes.

In another embodiment, the duration of immersion in the acid solution is at least 60 minutes.

In another embodiment, the temperature of the acid solution ranges between 10 and 80° C.

In another embodiment, the temperature of the acid solution ranges between 20 and 60° C.

In another embodiment, the temperature of the acid solution is in the range of 20 to 30° C.

In another embodiment, the temperature of the acid solution is in the range of 40 to 60° C.

In another embodiment, the acid solution comprises nitric acid.

In another embodiment, the acid solution comprises nitric acid, where the nitric acid concentration is between 5 and 60 vol. %.

In another embodiment, the acid solution comprises nitric acid, where the nitric acid concentration is between 20 and 45 vol. %.

In another embodiment, the acid solution comprises nitric acid, where the nitric acid concentration is between 15 and 30 vol. %.

In another embodiment, the acid solution comprises nitric acid, where the nitric acid concentration is between 20 and 25 vol. %.

In another embodiment, the chemical treatment solution comprises a chromate solution.

In another embodiment, the chemical treatment solution comprises sodium dichromate.

In another embodiment, the chemical treatment solution comprises sodium dichromate, where the sodium dichromate concentration is between 5 and 200 g/L.

In another embodiment, the chemical treatment solution comprises sodium dichromate, where the sodium dichromate concentration is between 10 and 100 g/L.

In another embodiment, the chemical treatment solution comprises a molybdate solution.

In another embodiment, the chemical treatment solution comprises disodium molybdate.

In another embodiment, the chemical treatment solution comprises disodium molybdate, where the disodium molybdate concentration is between 5 and 200 g/L.

In another embodiment, the chemical treatment solution comprises disodium molybdate, where the disodium molybdate concentration is between 10 and 100 g/L.

In another embodiment, the saline solution has a pH of at least 2.

In another embodiment, the saline solution has a pH of at least 4.

In another embodiment, the saline solution has a pH of at least 6.

In another embodiment, the saline solution has a concentration of NaCl of at least 0.1 g/L.

In another embodiment, the saline solution has a concentration of NaCl of at least 0.25 g/L.

In another embodiment, the saline solution has a concentration of NaCl of at least 1 g/L.

In another embodiment, the saline solution has a concentration of NaCl of at least 2 g/L.

In another embodiment, the saline solution has a concentration of NaCl of at least 5 g/L.

In another embodiment, the saline solution is a biological solution.

In another embodiment, the saline solution is saliva.

In another embodiment, the saline solution is perspiration.

In another embodiment, the saline solution is blood.

In another embodiment, the saline solution is a simulated body fluid.

In another embodiment, the saline solution is artificial saliva.

In another embodiment, the saline solution is artificial perspiration.

In another embodiment, the saline solution is artificial blood.

In another embodiment, the saline solution is sea water.

In another embodiment, the saline solution is simulated sea water.

In another embodiment, the metal moiety of the Ni-based metallic glass comprises at least one of Cr, Mo, Mn, Nb, Ta, Fe, Co, and Cu in its metal moiety.

In another embodiment, the metal moiety of the Ni-based metallic glass comprises at least Cr.

In another embodiment, the metal moiety of the Ni-based metallic glass comprises at least Mo.

In another embodiment, the metalloid moiety of the Ni-based metallic glass comprises at least one of P, B, and Si.

In another embodiment, the metalloid moiety of the Ni-based metallic glass comprises P and B.

In another embodiment, the metalloid moiety of the Ni-based metallic glass comprises P and Si.

In another embodiment, the metalloid moiety of the Ni-based metallic glass comprises Si and B.

In another embodiment, the Ni-based metallic glass comprises Cr and P.

In another embodiment, the Ni-based metallic glass is free of Ti.

In another embodiment, the passivated Ni-based metallic glass has a composition according to the following formula (subscripts denote atomic percent):

Ni_(100-a-b)X_(a)Z_(b)

where:

X is Cr, Mo, Mn, Nb, Ta, Fe, Co, Cu or combinations thereof;

Z is P, B, Si, or combinations thereof;

a is between 5 and 25; and

b is between 15 and 25.

In another embodiment, X is Cr and at least one of Nb and Ta, and Z is P and B.

In another embodiment, X is Cr and Nb, and Z is P and Si.

In another embodiment, X is Mo and at least one of Nb and Mn, and Z is P and B.

In another embodiment, X is Mo and at least one of Nb and Mn, and Z is P and Si.

In another embodiment, the passive layer has an amorphous structure.

In another embodiment, the passive layer of a surface-treated sample is thicker compared to the passive layer of an untreated sample.

In another embodiment the Ni-based metallic glass and/or passivated Ni-based metallic glass comprises Cr and P, and the passive layer of the surface-treated sample comprises O, P, and Cr.

In another embodiment the Ni-based metallic glass and/or passivated Ni-based metallic glass comprises Mo and P, and the passive layer of the surface-treated sample comprises O, P, and Mo.

In another embodiment, the passive layer of the surface-treated sample is poor in Ni.

In another embodiment, the average concentration of O within the passive layer of the surface-treated sample of a Ni-based metallic glass is higher than the concentration of O in an untreated sample.

In another embodiment, the average concentration of Ni within the passive layer of the surface treated sample of a Ni-based metallic glass and/or passivated Ni-based metallic glass is lower than the concentration of Ni in an untreated sample.

In another embodiment, the average concentration of P within the passive layer of the surface-treated sample of a Ni-based metallic glass and/or passivated Ni-based metallic glass comprising P is higher than the concentration of P in an untreated sample.

In another embodiment, the average concentration of Cr within the passive layer of the surface-treated sample of a Ni-based metallic glass and/or passivated Ni-based metallic glass comprising Cr is higher than the concentration of Cr in an untreated sample.

In another embodiment, the average concentration of O within the passive layer of the surface-treated sample of a Ni-based metallic glass and/or passivated Ni-based metallic glass comprising Cr and P is at least 5% higher than the concentration of O in an untreated sample.

In another embodiment, the average concentration of O within the passive layer of the surface-treated sample of a Ni-based metallic glass and/or passivated Ni-based metallic glass comprising Cr and P is at least 10% higher than the concentration of O in an untreated sample.

In another embodiment, the average concentration of O within the passive layer of the surface-treated sample of a Ni-based metallic glass and/or passivated Ni-based metallic glass comprising Cr and P is at least 20% higher than the concentration of O in an untreated sample.

In another embodiment, the average concentration of P within the passive layer of the surface-treated sample of a passivated Ni-based metallic glass comprising Cr and P is at least 5% higher than the concentration of P in an untreated sample.

In another embodiment, the average concentration of P within the passive layer of the surface-treated sample of a passivated Ni-based metallic glass comprising Cr and P is at least 10% higher than the concentration of P in an untreated sample.

In another embodiment, the average concentration of P within the passive layer of the surface-treated sample of a passivated Ni-based metallic glass comprising Cr and P is at least 20% higher than the concentration of P in an untreated sample.

In another embodiment, the average concentration of Cr within the passive layer of the surface-treated sample of a Ni-based metallic glass and/or passivated Ni-based metallic glass comprising Cr and P is at least 5% higher than the concentration of Cr in an untreated sample.

In another embodiment, the average concentration of Cr within the passive layer of the surface-treated sample of a Ni-based metallic glass and/or passivated Ni-based metallic glass comprising Cr and P is at least 10% higher than the concentration of Cr in an untreated sample.

In another embodiment, the average concentration of Cr within the passive layer of the surface-treated sample of a Ni-based metallic glass and/or passivated Ni-based metallic glass comprising Cr and P is at least 20% higher than the concentration of Cr in an untreated sample.

In another embodiment, the average concentration of Ni within the passive layer of the surface-treated sample of a Ni-based metallic glass and/or passivated Ni-based metallic glass comprising Cr and P is at least 5% lower than the concentration of Ni in an untreated sample.

In another embodiment, the average concentration of Ni within the passive layer of the surface-treated sample of a Ni-based metallic glass and/or passivated Ni-based metallic glass comprising Cr and P is at least 10% lower than the concentration of Ni in an untreated sample.

In another embodiment, the average concentration of Ni within the passive layer of the surface-treated sample of a Ni-based metallic glass and/or passivated Ni-based metallic glass comprising Cr and P is at least 20% lower than the concentration of Ni in an untreated sample.

In other embodiments, the passive layer of the surface-treated sample of a Ni-based metallic glass and/or passivated Ni-based metallic glass comprising Cr and P is thicker than the passive layer of an untreated sample.

In other embodiments, the passive layer of the surface-treated sample of a Ni-based metallic glass and/or passivated Ni-based metallic glass comprising Cr and P is at least 5% thicker than the passive layer of an untreated sample.

In another embodiment, the average concentration of Ni within the passive layer of the surface-treated sample of a Ni-based metallic glass and/or passivated Ni-based metallic glass comprising Cr and P is at least 10% lower than the concentration of Ni in an untreated sample.

In another embodiment, the average concentration of Ni within the passive layer of the surface-treated sample of a Ni-based metallic glass and/or passivated Ni-based metallic glass comprising Cr and P is at least 20% lower than the concentration of Ni in an untreated sample.

In another embodiment, the average concentration of O within the passive layer of the surface-treated sample of a Ni-based metallic glass and/or passivated Ni-based metallic glass comprising Cr and P that has been surface treated in a nitric acid solution of concentration of at least 15 vol. % for at least 30 minutes is at least 5% higher than the concentration of O in an untreated sample.

In another embodiment, the average concentration of O within the passive layer of the surface-treated sample of a Ni-based metallic glass and/or passivated Ni-based metallic glass comprising Cr and P that has been surface treated in a nitric acid solution of concentration of at least 15 vol. % for at least 30 minutes is at least 50% higher than the concentration of O in an untreated sample.

In another embodiment, the average concentration of P within the passive layer of the surface-treated sample of a passivated Ni-based metallic glass comprising Cr and P that has been surface treated in a nitric acid solution of concentration of at least 15 vol. % for at least 30 minutes is at least 10% higher than the concentration of P in an untreated sample.

In another embodiment, the average concentration of P within the passive layer of the surface-treated sample of a passivated Ni-based metallic glass comprising Cr and P that has been surface treated in a nitric acid solution of concentration of at least 15 vol. % for at least 30 minutes is at least 20% higher than the concentration of P in an untreated sample.

In another embodiment, the average concentration of Cr within the passive layer of the surface-treated sample of a Ni-based metallic glass and/or passivated Ni-based metallic glass comprising Cr and P that has been surface treated in a nitric acid solution of concentration of at least 15 vol. % for at least 30 minutes is at least 15% higher than the concentration of Cr in an untreated sample.

In another embodiment, the average concentration of Cr within the passive layer of the surface-treated sample of a Ni-based metallic glass and/or passivated Ni-based metallic glass comprising Cr and P that has been surface treated in a nitric acid solution of concentration of at least 15 vol. % for at least 30 minutes is at least 15% higher than the concentration of Cr in an untreated sample.

In another embodiment, the average concentration of Ni within the passive layer of the surface-treated sample of a Ni-based metallic glass and/or passivated Ni-based metallic glass comprising Cr and P that has been surface treated in a nitric acid solution of concentration of at least 15 vol. % for at least 30 minutes is at least 5% lower than the concentration of Ni in an untreated sample.

In another embodiment, the average concentration of Ni within the passive layer of the surface-treated sample of a Ni-based metallic glass and/or passivated Ni-based metallic glass comprising Cr and P that has been surface treated in a nitric acid solution of concentration of at least 15 vol. % for at least 30 minutes is at least 10% lower than the concentration of Ni in an untreated sample.

In other embodiments, the passive layer of the surface-treated sample of a Ni-based metallic glass and/or passivated Ni-based metallic glass comprising Cr and P that has been surface treated in a nitric acid solution of concentration of at least 15 vol. % for at least 30 minutes is thicker than the passive layer of an untreated sample.

In other embodiments, the passive layer of the surface-treated sample of a Ni-based metallic glass and/or passivated Ni-based metallic glass comprising Cr and P that has been surface treated in a nitric acid solution of concentration of at least 15 vol. % for at least 30 minutes is at least 5% thicker than the passive layer of an untreated sample.

In other embodiments, the passive layer of the surface-treated sample of a Ni-based metallic glass and/or passivated Ni-based metallic glass comprising Cr and P that has been surface treated in a nitric acid solution of concentration of at least 15 vol. % for at least 30 minutes is at least 10% thicker than the passive layer of an untreated sample.

In other embodiments, the passive layer of the surface-treated sample of a Ni-based metallic glass and/or passivated Ni-based metallic glass comprising Cr and P that has been surface treated in a nitric acid solution of concentration of at least 15 vol. % for at least 30 minutes is at least 25% thicker than the passive layer of an untreated sample.

The disclosure is also directed to a Ni-based metallic glass and/or passivated Ni-based metallic glass comprising an inner bulk material portion, and an outer passive layer portion. The Ni-based metallic glass and/or passivated Ni-based metallic glass comprise at least one of Cr and Mo. The average atomic concentration of Cr and/or Mo within the passive layer portion is higher than the respective concentrations in the inner bulk material portion.

In another embodiment, the average atomic concentration of Cr and/or Mo within the passive layer is at least 2% higher than the respective concentrations in the inner bulk material portion.

In another embodiment, the average atomic concentration of Cr and/or Mo within the passive layer is at least 5% higher than the respective concentrations in the inner bulk material portion.

In another embodiment, the average atomic concentration of Cr and/or Mo within the passive layer is at least 10% higher than the respective concentrations in the inner bulk material portion.

In another embodiment, the average atomic concentration of Cr and/or Mo within the passive layer is at least 20% higher than the respective concentrations in the inner bulk material portion.

The disclosure is also directed to a Ni-based metallic glass and/or passivated Ni-based metallic glass comprising an inner bulk material portion, and an outer passive layer portion. The Ni-based metallic glass and/or passivated Ni-based metallic glass comprise P. The average atomic concentration of P within the passive layer portion is higher than the P concentration in the inner bulk material portion. In some variations, the inner bulk material portion that comprises Cr and P and an outer passive layer portion that comprises Cr, P, and O.

In some variations, the inner bulk material portion comprises Mo and P and the outer passive layer comprises Mo, P, and O. In some variations, the average atomic concentration of Cr and Mo in the outer passive layer is at least 2% higher than the average atomic concentration of Cr and Mo in the inner bulk material portion. In some variations, the average atomic concentration of P in the outer passive layer is at least 5% higher than the average atomic concentration of P in the inner bulk material portion.

In another embodiment, the average atomic concentration of P within the passive layer is at least 5% higher than the P concentration in the inner bulk material portion.

In another embodiment, the average atomic concentration of P within the passive layer is at least 10% higher than the P concentration in the inner bulk material portion.

In another embodiment, the average atomic concentration of P within the passive layer is at least 20% higher than the respective concentration in the inner bulk material portion.

In another embodiment, the average atomic concentration of P within the passive layer is at least 30% higher than the respective concentration in the inner bulk material portion.

The disclosure is also directed to an article of a passivated Ni-based metallic glass.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 provides a plot showing the effect of surface treatment in a Nitric acid solution on the Nickel-ion release rate of Ni_(71.4)Cr_(5.52)Nb_(3.38)P_(16.67)B_(3.03) metallic glass in a PBS (Phosphate Buffered Solution) solution in accordance with embodiments.

FIG. 2 provides a plot showing the effect of surface treatment in a Citric acid solution on the Nickel-ion release rate of Ni_(71.4)Cr_(5.52)Nb_(3.38)P_(16.67)B_(3.03) metallic glass in a PBS (Phosphate Buffered Solution) solution in accordance with embodiments.

FIG. 3 provides a plot showing the effect of surface treatment in a Nitric acid solution on the Nickel-ion release rate of Ni_(68.17)Cr_(8.65)Nb_(2.98)P_(16.42)B_(3.28)Si_(0.5) metallic glass in a PBS (Phosphate Buffered Solution) solution in accordance with embodiments.

FIG. 4 provides a plot showing the effect of surface treatment on the weekly Nickel-ion release rate of Ni_(68.17)Cr_(8.65)Nb_(2.98)P_(16.42)B_(3.28)Si_(0.5) metallic glass in an artificial perspiration solution.

FIG. 5 provides a plot of depth profile up to 200 angstrom for the concentration of Oxygen on the surfaces of an as-polished sample and samples surface treated in nitric acid solutions at various acid concentrations, as detected by XPS in accordance with embodiments.

FIG. 6 provides a plot of depth profile up to 200 angstrom for the concentration of Phosphorus/Boron on the surfaces of an as-polished and samples surface treated in nitric acid solutions at various acid concentrations, as detected by XPS in accordance with embodiments.

FIG. 7 provides a plot of depth profile up to 200 angstrom for the concentration of Chromium on the surfaces of an as-polished sample and samples surface treated in nitric acid solutions at various acid concentrations, as detected by XPS in accordance with embodiments.

FIG. 8 provides a plot of depth profile up to 200 angstrom for the concentration of Niobium on the surfaces of an as-polished sample and samples surface treated in nitric acid solutions at various acid concentrations, as detected by XPS in accordance with embodiments.

FIG. 9 provides a plot of depth profile up to 200 angstrom for the concentration of Nickel on the surfaces of an as-polished sample and samples surface treated in nitric acid solutions at various acid concentrations, as detected by XPS in accordance with embodiments.

FIG. 10 provides a plot of depth profile up to 200 angstrom for the concentration of Oxygen on the surfaces of an as-polished sample and a sample surface treated in a 20 vol. % nitric acid solution, as detected by SIMS in accordance with embodiments. The insets provide plots of depth profile up to 60 angstrom for the detected Oxygen, and the regions for the “organic layer,” “passive layer,” and “bulk material” are designated by arrows. The “bulk material” designation in the figures refers to the inner bulk material portion.

FIG. 11 provides a plot of depth profile up to 200 angstrom for the concentration of Phosphorus on the surfaces of an as-polished sample and a sample surface treated in a 20 vol. % nitric acid solution, as detected by SIMS in accordance with embodiments. The insets provide plots of depth profile up to 60 angstrom for the detected Phosphorus, and the regions for the “organic layer,” “passive layer,” and “bulk material” are designated by arrows.

FIG. 12 provides a plot of depth profile up to 200 angstrom for the concentration of Chromium on the surfaces of an as-polished sample and a sample surface treated in a 20 vol. % nitric acid solution, as detected by SIMS in accordance with embodiments. The insets provide plots of depth profile up to 60 angstrom for the detected Chromium, and the regions for the “organic layer,” “passive layer,” and “bulk material” are designated by arrows.

FIG. 13 provides a plot of depth profile up to 200 angstrom for the concentration of Niobium on the surfaces of an as-polished sample and a sample surface treated in a 20 vol. % nitric acid solution, as detected by SIMS in accordance with embodiments. The insets provide plots of depth profile up to 60 angstrom for the detected Niobium, and the regions for the “organic layer,” “passive layer,” and “bulk material” are designated by arrows.

FIG. 14 provides a plot of depth profile up to 200 angstrom for the concentration of Boron on the surfaces of an as-polished sample and a sample surface treated in a 20 vol. % nitric acid solution, as detected by SIMS in accordance with embodiments. The insets provide plots of depth profile up to 60 angstrom for the detected Boron, and the regions for the “organic layer,” “passive layer,” and “bulk material” are designated by arrows.

FIG. 15 provides a plot of depth profile up to 200 angstrom for the concentration of Silicon on the surfaces of an as-polished sample and a sample surface treated in a 20 vol. % nitric acid solution, as detected by SIMS in accordance with embodiments. The insets provide plots of depth profile up to 60 angstrom for the detected Silicon, and the regions for the “organic layer,” “passive layer,” and “bulk material” are designated by arrows.

FIG. 16 provides a plot of depth profile up to 200 angstrom for the concentration of Nickel on the surfaces of an as-polished sample and a sample surface treated in a 20 vol. % nitric acid solution, as detected by SIMS in accordance with embodiments. The insets provide plots of depth profile up to 60 angstrom for the detected Nickel, and the regions for the “organic layer,” “passive layer,” and “bulk material” are designated by arrows.

FIG. 17 provides a plot of depth profile up to 350 angstrom for the concentration of Oxygen on the surfaces of an as-polished sample and a sample surface treated in a 50 g/L sodium dichromate solution, as detected by SIMS in accordance with embodiments. The insets provide plots of depth profile up to 100 angstrom for the detected Oxygen, and the “passive layer” region for each sample is designated by an arrow (solid arrow designates the “passive layer” region of the as-polished sample, while broken arrow designates the “passive layer” region of the surface treated sample).

FIG. 18 provides a plot of depth profile up to 350 angstrom for the concentration of Phosphorus on the surfaces of an as-polished sample and a sample surface treated in a 50 g/L sodium dichromate solution, as detected by SIMS in accordance with embodiments. The insets provide plots of depth profile up to 100 angstrom for the detected Phosphorus, and the “passive layer” region for each sample is designated by an arrow (solid arrow designates the “passive layer” region of the as-polished sample, while broken arrow designates the “passive layer” region of the surface treated sample).

FIG. 19 provides a plot of depth profile up to 350 angstrom for the concentration of Chromium on the surfaces of an as-polished sample and a sample surface treated in a 50 g/L sodium dichromate solution, as detected by SIMS in accordance with embodiments. The insets provide plots of depth profile up to 100 angstrom for the detected Chromium, and the “passive layer” region for each sample is designated by an arrow (solid arrow designates the “passive layer” region of the as-polished sample, while broken arrow designates the “passive layer” region of the surface treated sample).

FIG. 20 provides a plot of depth profile up to 350 angstrom for the concentration of Niobium on the surfaces of an as-polished sample and a sample surface treated in a 50 g/L sodium dichromate solution, as detected by SIMS in accordance with embodiments. The insets provide plots of depth profile up to 100 angstrom for the detected Niobium, and the “passive layer” region for each sample is designated by an arrow (solid arrow designates the “passive layer” region of the as-polished sample, while broken arrow designates the “passive layer” region of the surface treated sample).

FIG. 21 provides a plot of depth profile up to 350 angstrom for the concentration of Boron on the surfaces of an as-polished sample and a sample surface treated in a 50 g/L sodium dichromate solution, as detected by SIMS in accordance with embodiments. The insets provide plots of depth profile up to 100 angstrom for the detected Boron, and the “passive layer” region for each sample is designated by an arrow (solid arrow designates the “passive layer” region of the as-polished sample, while broken arrow designates the “passive layer” region of the surface treated sample).

FIG. 22 provides a plot of depth profile up to 350 angstrom for the concentration of Silicon on the surfaces of an as-polished sample and a sample surface treated in a 50 g/L sodium dichromate solution, as detected by SIMS in accordance with embodiments. The insets provide plots of depth profile up to 100 angstrom for the detected Silicon, and the “passive layer” region for each sample is designated by an arrow (solid arrow designates the “passive layer” region of the as-polished sample, while broken arrow designates the “passive layer” region of the surface treated sample).

FIG. 23 provides a plot of depth profile up to 350 angstrom for the concentration of Nickel on the surfaces of an as-polished sample and a sample surface treated in a 50 g/L sodium dichromate solution, as detected by SIMS in accordance with embodiments. The insets provide plots of depth profile up to 100 angstrom for the detected Nickel, and the “passive layer” region for each sample is designated by an arrow (solid arrow designates the “passive layer” region of the as-polished sample, while broken arrow designates the “passive layer” region of the surface treated sample).

FIG. 24 provides a plot of depth profile up to 200 angstrom for the concentration of Oxygen on the surfaces of an as-polished sample and a sample surface treated by a two-step chemical solution treatment (the first solution comprises 20 volume % nitric acid combined with 25 g/L sodium dichromate, and the second solution comprises 50 g/L sodium dichromate), as detected by SIMS in accordance with embodiments. The insets provide plots of depth profile up to 60 angstrom for the detected Oxygen, and the “passive layer” region for each sample is designated by an arrow (solid arrow designates the “passive layer” region of the as-polished sample, while broken arrow designates the “passive layer” region of the surface treated sample).

FIG. 25 provides a plot of depth profile up to 200 angstrom for the concentration of Phosphorus on the surfaces of an as-polished sample and a sample surface treated by a two-step chemical solution treatment (the first solution comprises 20 volume % nitric acid combined with 25 g/L sodium dichromate, and the second solution comprises 50 g/L sodium dichromate), as detected by SIMS in accordance with embodiments. The insets provide plots of depth profile up to 60 angstrom for the detected Phosphorus, and the “passive layer” region for each sample is designated by an arrow (solid arrow designates the “passive layer” region of the as-polished sample, while broken arrow designates the “passive layer” region of the surface treated sample).

FIG. 26 provides a plot of depth profile up to 200 angstrom for the concentration of Chromium on the surfaces of an as-polished sample and a sample surface treated by a two-step chemical solution treatment (the first solution comprises 20 volume % nitric acid combined with 25 g/L sodium dichromate, and the second solution comprises 50 g/L sodium dichromate), as detected by SIMS in accordance with embodiments. The insets provide plots of depth profile up to 60 angstrom for the detected Chromium, and the “passive layer” region for each sample is designated by an arrow (solid arrow designates the “passive layer” region of the as-polished sample, while broken arrow designates the “passive layer” region of the surface treated sample).

FIG. 27 provides a plot of depth profile up to 200 angstrom for the concentration of Niobium on the surfaces of an as-polished sample and a sample surface treated by a two-step chemical solution treatment (the first solution comprises 20 volume % nitric acid combined with 25 g/L sodium dichromate, and the second solution comprises 50 g/L sodium dichromate), as detected by SIMS in accordance with embodiments. The insets provide plots of depth profile up to 60 angstrom for the detected Niobium, and the “passive layer” region for each sample is designated by an arrow (solid arrow designates the “passive layer” region of the as-polished sample, while broken arrow designates the “passive layer” region of the surface treated sample).

FIG. 28 provides a plot of depth profile up to 200 angstrom for the concentration of Boron on the surfaces of an as-polished sample and a sample surface treated by a two-step chemical solution treatment (the first solution comprises 20 volume % nitric acid combined with 25 g/L sodium dichromate, and the second solution comprises 50 g/L sodium dichromate), as detected by SIMS in accordance with embodiments. The insets provide plots of depth profile up to 60 angstrom for the detected Boron, and the “passive layer” region for each sample is designated by an arrow (solid arrow designates the “passive layer” region of the as-polished sample, while broken arrow designates the “passive layer” region of the surface treated sample).

FIG. 29 provides a plot of depth profile up to 200 angstrom for the concentration of Silicon on the surfaces of an as-polished sample and a sample surface treated by a two-step chemical solution treatment (the first solution comprises 20 volume % nitric acid combined with 25 g/L sodium dichromate, and the second solution comprises 50 g/L sodium dichromate), as detected by SIMS in accordance with embodiments. The insets provide plots of depth profile up to 60 angstrom for the detected Silicon, and the “passive layer” region for each sample is designated by an arrow (solid arrow designates the “passive layer” region of the as-polished sample, while broken arrow designates the “passive layer” region of the surface treated sample).

FIG. 30 provides a plot of depth profile up to 200 angstrom for the concentration of Nickel on the surfaces of an as-polished sample and a sample surface treated by a two-step chemical solution treatment (the first solution comprises 20 volume % nitric acid combined with 25 g/L sodium dichromate, and the second solution comprises 50 g/L sodium dichromate), as detected by SIMS in accordance with embodiments. The insets provide plots of depth profile up to 60 angstrom for the detected Nickel, and the “passive layer” region for each sample is designated by an arrow (solid arrow designates the “passive layer” region of the as-polished sample, while broken arrow designates the “passive layer” region of the surface treated sample).

FIG. 31 presents a plot of the logarithm of the Ni ion release rate in units of μg/cm²/week against the average atomic concentration of Cr in the passive layer in units of atomic percent. The line is a power-law fit through the data.

DETAILED DESCRIPTION

The disclosure is directed to methods of chemical surface treatment for Ni-based metallic glasses to reduce the amount of Ni release when the metallic glass is exposed to a saline containing environment. Embodiments of the chemical surface treatment methods improve the corrosion resistance of Ni-based metallic glasses in biological, physiological, and other saline-containing environments by protecting the material with a stable passive layer that acts as a barrier coating against Ni ion release.

Chemical surface treatments are generally applied in order to encourage passivation of a material by promoting surface oxidation and by dissolving foreign materials that might be present on the surface of the material from previous operations. Rapid passivation of the material will provide corrosion resistance when exposed to a corrosive environment, and prevent leaching of the various elemental constituents of the material into the corrosive environment.

The surface oxide layer increases the stability of the surface layers by protecting the bulk material from corrosion, and creates a physical and chemical barrier against Ni oxidation by modifying the oxidation pathways of Ni.

The applicability of a surface treatment to promote rapid passivation by surface oxidation depends strongly on the chemistry between the elemental constituents of the alloy and the chemical treatment solution, as well as on the chemistry between the formed surface oxide layer and the corrosive environment, making it difficult to predict the applicability of a surface treatment between different classes of materials. For example, chemical surface treatment for chrome containing stainless steel has been well studied, and it has been determined that the type and nature of surface treatment that can promote passivation depends on factors such as the chrome content and the physical characteristics of the stainless steel (such as machinability). Moreover, improper chemical treatment can actually induce corrosion in the sample.

The applicability of the surface treatment also depends on the atomic structure of the material, as well as that of the surface oxide layer. Again, using the example of chrome containing stainless steel as a benchmark, it has been found that the type of chemical treatment that promotes passivation changes depending on the crystal structure of the stainless steel. For example, stainless steels with austenitic, ferritic, or martensitic crystal structures require very specific chemical treatment processes (e.g. solution chemistry, additives, solution temperature, etc.) to successfully promote passivation. In certain instances, certain chemical treatments that work for some crystal structures don't work for others (e.g. citric acid works for ferritic type Chrome Core 18FM but not nitric acid; by contrast, nitric acid works for ferritic types 430F and 430FR but not citric acid) (DeBold, Terry A. & Martin, James W. “How To Passivate Stainless Steel Parts” Modern Machine Shop, Oct. 1, 2003). Moreover, inappropriate chemical treatment of stainless steels may cause “flash attacks”, where instead of passivating the material by obtaining the desired oxide film, which typically appears as a shiny and clean surface layer, a heavily etched or darkened surface layer is produced. This causes degradation of the surface rather than passivation, and generally leads to higher corrosion rates.

Because the promotion of passivation depends intimately on the crystalline structure of the sample and the chemistry occurring between the chemical treatment solution and the sample, this unpredictability is heightened when chemical surface treatments are attempted on a non-crystalline material, such as a metallic glass (i.e. an amorphous metal). In one example, discussed in U.S. Pat. Pub. No. 2009/0014096, samples of Zr—Ti based amorphous alloys containing one or more of Ni, Cu, Co, Fe, Cr and Be were tested for corrosion resistance in acid baths. The studies showed that, rather than promoting passivation, many of these materials corroded very rapidly in the acidic environment. Moreover, the publication states that exposure to acidic environments for Ni and Cu alloys particularly should be avoided. Indeed, amorphous alloys containing these elements have been shown to dissolve almost immediately when exposed to an acidic environment. (U.S. Pat. Pub. No. 2009/0014096, the disclosure of which is incorporated herein by reference.) To date, passivation of a material that has an amorphous atomic structure, and specifically a Ni-based metallic glass, by a chemical surface treatment has not been implemented. Accordingly, chemical surface treatment methods for promoting the passivation of Ni-based metallic glasses need to be developed.

Many embodiments are directed to methods of surface treatment for Ni-based alloys, i.e. to alloys that comprise Ni at an atomic fraction of at least 50%, in order to reduce the amount of Ni ion release when the alloy is exposed to a corrosive environment. With respect to the structure of the material, embodiments are directed to metallic materials that have an amorphous structure, i.e. to Ni-based metallic glasses. With respect to the chemical composition of the material, in one embodiment, the metal moiety of the Ni-based metallic glass comprises at least one of Cr, Mo, Mn, Nb, Ta, Fe, Co, and Cu. In another embodiment, the metal moiety of the Ni-based metallic glass comprises at least Cr. In another embodiment, the metal moiety of the Ni-based metallic glass comprises at least Mo. In another embodiment, the metalloid moiety of the Ni-based metallic glass comprises at least one of P, B, and Si. In another embodiment, the metalloid moiety of the Ni-based metallic glass comprises P and B. In another embodiment, the metalloid moiety of the Ni-based metallic glass comprises P and Si. In another embodiment, the metalloid moiety of the Ni-based metallic glass comprises Si and B. In another embodiment, the Ni-based metallic glass is free of Ti.

In another embodiment, the Ni-based metallic glass and/or passivated Ni-based metallic glass has a composition according to the following formula (subscripts denote atomic percent):

Ni_(100-a-b)X_(a)Z_(b)

where:

X is Cr, Mo, Mn, Nb, Ta, Fe, Co, Cu or combinations thereof;

Z is P, B, Si, or combinations thereof;

a is between 5 and 25; and

b is between 15 and 25.

In another embodiment, X is Cr and at least one of Nb and Ta, and Z is P and B. In another embodiment, X is Cr and Nb, and Z is P and Si. In another embodiment, X is Mo and at least one of Nb and Mn, and Z is P and B. In another embodiment, X is Mo and at least one of Nb and Mn, and Z is P and Si. Example Ni-based metallic glass alloy systems include, but are not limited to, Ni—Cr—Nb—P—B, Ni—Co—Cr—Nb—P—B, Ni—Fe—Cr—Nb—P—B, Ni—Cu—Cr—Nb—P—B, Ni—Cr—Nb—P—Si, Ni—Cr—Ta—P—B, Ni—Cr—Mn—P—B, Ni—Mo—Nb—Mn—P—B, Ni—Mo—Nb—Mn—P—Si, Ni—Mn—Nb—P—B, Ni—Mn—Nb—P—Si, Ni—Cr—Mn—Nb—P—B, Ni—Cr—Mn—Mo—P—B, Ni—Mn—Ta—P—B, Ni—Cr—Si—B—P, Ni—Cr—Mo—Si—B—P, and Ni—Fe—Si—B—P.

In another embodiment, the Ni-based metallic glass and/or passivated Ni-based metallic glass has a chemical composition represented by the following formula (subscripts denote atomic percent):

Ni_((100-a-b-c-d))Cr_(a)Nb_(b)P_(c)B_(d)

where,

a is greater than 3 and less than 15;

b is greater than 1.5 and less than 4.5;

c is greater than 14.5 and less than 18.5; and

is greater than 1 and less than 5,

as described in U.S. Pat. No. 9,085,814 entitled “Bulk Nickel-Based Chromium and Phosphorus Bearing Metallic Glasses,” which is incorporated herein by reference in its entirety.

In another embodiment, the Ni-based metallic glass and/or passivated Ni-based metallic glass has a chemical composition represented by the following formula (subscripts denote atomic percent):

Ni_((69-w-x-y-z))Cr_(8.5+w)Nb_(3+x)P_(16.5+y)B_(3+z)

where w, x, y, and z can be positive or negative, and where,

0.0494w ²+1.78x ²+4y ² +z ²<1,

as described in U.S. Pat. No. 9,085,814 entitled “Bulk Nickel-Based Chromium and Phosphorus Bearing Metallic Glasses,” which is incorporated herein by reference in its entirety.

In yet another embodiment, the Ni-based metallic glass and/or passivated Ni-based metallic glass has a composition according to the following formula (subscripts denote atomic percent):

Ni_((100-a-b-c-d))Cr_(a)Nb_(b)P_(c)B_(d)

where:

a ranges from 3 to 13;

b is determined by x−y*a, where x ranges from 3.8 to 4.2 and y ranges from 0.11 to 0.14;

c ranges from 16.25 to 17;

d ranges from 2.75 to 3.5,

as described in U.S. Pat. Pub. No. 2014/0116579, entitled “Bulk Nickel-Based Chromium and Phosphorus Metallic Glasses with High Toughness,” filed on Oct. 30, 2013, which is incorporated herein by reference in its entirety.

In yet another embodiment, the Ni-based metallic glass and/or passivated Ni-based metallic glass has a chemical composition represented by the passivated Ni-based metallic glass has a composition according to the following formula (subscripts denote atomic percent):

Ni_((100-a-b-c-d))Cr_(a)Nb_(b)P_(c)B_(d)

where:

a ranges from 7 to 11;

b ranges from 1 to 3.25;

c ranges from 13 to 16; and

d ranges from 3 to 6.5,

as described in U.S. Pat. Pub. No. 2015/0240,336, entitled “Bulk Nickel-Chromium-Phosphorus Glasses Bearing Niobium and Boron Exhibiting High Strength and/or High Thermal Stability of the Supercooled Liquid,” filed on Nov. 13, 2014, which is incorporated herein by reference in its entirety.

In yet another embodiment, the Ni-based metallic glass and/or passivated Ni-based metallic glass has a chemical composition according to the following formula (subscripts denote atomic percent):

Ni_((100-a-b-c-d))Cr_(a)Nb_(b)P_(c)B_(d)

where:

a ranges from 7 to 11;

b ranges from 4.5 to 5.5;

c ranges from 13 to 16; and

d ranges from 4.5 to 5.5,

as described in U.S. Pat. Pub. No. 2015/0240,336, entitled “Bulk Nickel-Chromium-Phosphorus Glasses Bearing Niobium and Boron Exhibiting High Strength and/or High Thermal Stability of the Supercooled Liquid,” filed on Nov. 13, 2014, which is incorporated herein by reference in its entirety.

In yet another embodiment, the Ni-based metallic glass and/or passivated Ni-based metallic glass has a chemical composition according to the following formula (subscripts denote atomic percent):

Ni_((100-a-b-c-d-e))X_(a)Cr_(b)Nb_(c)P_(d)B_(e)

where:

a ranges from 0.5 to 30;

b ranges from 2 to 15;

c ranges from 1 to 5;

d ranges from 14 to 19;

e ranges from 1 to 5; and

wherein X can be at least one of Co, Fe, and Cu,

as described in U.S. Pat. Pub. No. 2015/0176111, entitled “Bulk Nickel-Iron-Based, Nickel-Cobalt-Based and Nickel-Copper-Based Glasses Bearing Chromium, Niobium, Phosphorus and Boron,” filed on Dec. 23, 2014, which is incorporated herein by reference in its entirety.

In yet another embodiment, the Ni-based metallic glass and/or passivated Ni-based metallic glass has a chemical composition according to the following formula (subscripts denote atomic percent):

Ni_((100-a-b-c-d))Cr_(a)Ta_(b)P_(c)B_(d)

where:

a is between 3 and 11;

b is between 1.75 and 4;

c is between 14 and 17.5; and

d is between 2.5 and 5,

as described in U.S. Pat. Pub. No. 2014/0130945, entitled “Bulk Nickel-Phosphorus-Boron Glasses Bearing Chromium and Tantalum,” filed on Nov. 15, 2013, which is incorporated herein by reference in its entirety.

In yet another embodiment, the Ni-based metallic glass and/or passivated Ni-based metallic glass has a chemical composition according to the following formula (subscripts denote atomic percent):

Ni_((100-a-b-c-d-e))Co_(a)Cr_(b)Ta_(c)P_(d)B_(e)

where:

a ranges from 0.5 to 40;

b ranges from 3 to 11;

c ranges from 1.5 to 4;

d ranges from 14 to 17.5;

e ranges from 2 to 5; and

wherein X can be at least one of Co, Fe, and Cu,

as described in U.S. patent application Ser. No. 14/501,779, entitled “Bulk Nickel-Cobalt-Based Glasses Bearing Chromium, Tantalum, Phosphorus and Boron,” filed on Sep. 30, 2014, which is incorporated herein by reference in its entirety.

In yet another embodiment, the Ni-based metallic glass and/or passivated Ni-based metallic glass has a chemical composition according to the following formula (subscripts denote atomic percent):

Ni_((100-a-b-c-d))Cr_(a)Nb_(b)P_(c)Si_(d)

where:

a is between 2 and 18;

b is between 1 and 6;

c is between 16 and 20; and

d is up to 4,

as described in U.S. Pat. Pub. No. 2015/0159242, entitled “Bulk Nickel-Based Glasses Bearing Chromium, Niobium, Phosphorus, and Silicon,” filed Dec. 9, 2014, which is incorporated by reference in its entirety.

In yet another embodiment, the Ni-based metallic glass and/or passivated Ni-based metallic glass has a chemical composition according to the following formula (subscripts denote atomic percent):

Ni_((100-a-b-c))Mn_(a)X_(b)P_(c)Si_(d)

where:

a is between 0.25 and 12;

b is up to 15;

c is between 14 and 22;

d is between 0.25 and 5; and

wherein X can be at least one of Cr and Mo,

as described in U.S. Provisional Patent Application No. 61/913,684, entitled “Bulk Nickel-Phosphorus-Silicon Glasses Bearing Manganese,” filed Nov. 11, 2014, which is incorporated by reference in its entirety.

In yet another embodiment, the Ni-based metallic glass and/or passivated Ni-based metallic glass has a composition according to the following formula (subscripts denote atomic percent):

Ni_((100-a-b-c))Mn_(a)X_(b)P_(c)B_(d)

where:

a is between 0.5 and 10;

b is up to 15;

c is between 14 and 24;

d is between 1 and 8; and

wherein X can be at least one of Cr and Mo,

as described in U.S. Pat. Pub. No. 2014/0238551, entitled “Bulk Nickel-Phosphorus-Boron Glasses Bearing Manganese,” filed Feb. 26, 2014, which is incorporated by reference in its entirety.

In yet another embodiment, the Ni-based metallic glass and/or passivated Ni-based metallic glass has a chemical composition according to the following formula (subscripts denote atomic percent):

N_((100-a-b-c-d))Mo_(a)Nb_(b)P_(c)B_(d)

where:

a is between 2 and 12;

b is up to 8;

c is between 14 and 19; and

d is between 1 and 4,

as described in U.S. Pat. Pub. No. 2014/0096873, entitled “Bulk Nickel-Phosphorus-Boron Glasses Bearing Molybdenum,” filed Feb. 26, 2014, which is incorporated by reference in its entirety.

In yet another embodiment, the Ni-based metallic glass and/or passivated Ni-based metallic glass has a chemical composition according to the following formula (subscripts denote atomic percent):

Ni_((100-a-b-c-d-e))Mo_(a)Nb_(b)Mn_(c)P_(d)B_(e)

where:

a is between 1 and 5;

b is between 3 and 5;

c is up to 2;

d is between 16 and 17; and

e is between 2.75 and 3.75,

as described in U.S. Pat. Pub. No. 2014/0096873, entitled “Bulk Nickel-Phosphorus-Boron Glasses Bearing Molybdenum,” filed Feb. 26, 2014, which is incorporated by reference in its entirety.

In yet another embodiment, the Ni-based metallic glass and/or passivated Ni-based metallic glass has a chemical composition according to the following formula (subscripts denote atomic percent):

Ni_((100-a-b-c-d-e))Cr_(a)Mo_(b)Si_(c)B_(d)P_(e)

where:

a is between 3.5 and 6

b is up to 2,

c is between 4.5 and 7,

d is between 10.5 and 13, and

e is between 4 and 6,

as described in U.S. Pat. Pub. No. 2014/0076467, entitled “Bulk Nickel-Silicon-Boron Glasses Bearing Chromium,” filed Sep. 17, 2013, which is incorporated by reference in its entirety.

With respect to the chemistry of the passive layer of the surface-treated sample, in one embodiment, where the Ni-based metallic glass comprises Cr and P, the passive layer of the treated sample comprises oxygen, P, and Cr. In another embodiment, where the Ni-based metallic glass comprises Cr and P, the passive layer of the treated sample comprises oxides and phosphides of Cr. In another embodiment, where the Ni-based metallic glass comprises Cr, P and B, the passive layer of the treated sample comprises oxygen, P and/or B, and Cr. In another embodiment, where the Ni-based metallic glass comprises Cr and P and B, the passive layer of the treated sample comprises oxides and phosphides and/or borides of Cr. In another embodiment, where the Ni-based metallic glass comprises Mo and P, the passive layer of the treated sample comprises oxygen, P, and Mo. In another embodiment, where the Ni-based metallic glass comprises Mo and P, the passive layer of the treated sample comprises oxides and phosphides of Mo. In another embodiment, where the Ni-based metallic glass comprises Mo, P and B, the passive layer of the treated sample comprises oxygen, P and/or B, and Mo. In another embodiment, where the Ni-based metallic glass comprises Mo and P and B, the passive layer of the treated sample comprises oxides and phosphides and/or borides of Mo. In another embodiment, where the Ni-based metallic glass comprises Cr and Si, the passive layer of the treated sample comprises oxygen, Si, and Cr. In another embodiment, where the Ni-based metallic glass comprises Cr and Si, the passive layer of the treated sample comprises oxides and silicides of Cr. In another embodiment, where the Ni-based metallic glass comprises Cr, Si and B, the passive layer of the treated sample comprises oxygen, Si and/or B, and Cr. In another embodiment, where the Ni-based metallic glass comprises Cr, Si and B, the passive layer of the treated sample comprises oxides and silicides and/or borides of Cr. In another embodiment, where the Ni-based metallic glass comprises Mo and Si, the passive layer of the treated sample comprises oxygen, Si, and Mo. In another embodiment, where the Ni-based metallic glass comprises Mo and Si, the passive layer of the treated sample comprises oxides and silicides of Mo. In another embodiment, where the Ni-based metallic glass comprises Mo, Si and B, the passive layer of the treated sample comprises oxygen, Si and/or B, and Mo. In another embodiment, where the Ni-based metallic glass comprises Mo, Si and B, the passive layer of the treated sample comprises oxides and silicides and/or borides of Mo. In another embodiment, the passive layer of the treated sample is poor in Ni.

With respect to the atomic structure of the surface oxide layer, in one embodiment, the surface oxide layer has an amorphous structure.

With respect to the chemical treatment solution, the disclosure is directed to a chemical treatment solution that may be an acid solution, a chromate solution, a molybdate solution, or combinations thereof.

In one embodiment, the chemical treatment solution comprises an acid solution. In another embodiment, the chemical treatment solution comprises nitric acid. In another embodiment, the chemical treatment solution comprises nitric acid, where the nitric acid concentration is between 5 and 60 vol. %. In another embodiment, the chemical treatment solution comprises nitric acid, where the nitric acid concentration is between 20 and 45 vol. %. In another embodiment, the chemical treatment solution comprises nitric acid, where the nitric acid concentration is between 15 and 30 vol. %. In another embodiment, the chemical treatment solution comprises nitric acid, where the nitric acid concentration is between 20 and 25 vol. %.

In another embodiment, the chemical treatment solution comprises a chromate solution. In another embodiment, the chemical treatment solution comprises sodium dichromate. In another embodiment, the chemical treatment solution comprises sodium dichromate, where the sodium dichromate concentration is between 5 and 200 g/L. In another embodiment, the chemical treatment solution comprises sodium dichromate, where the sodium dichromate concentration is between 10 and 100 g/L.

In another embodiment, the chemical treatment solution comprises a molybdate solution. In another embodiment, the chemical treatment solution comprises disodium molybdate. In another embodiment, the chemical treatment solution comprises disodium molybdate, where the disodium molybdate concentration is between 5 and 200 g/L. In another embodiment, the chemical treatment solution comprises disodium molybdate, where the disodium molybdate concentration is between 10 and 100 g/L.

With respect to the corrosive environment, many embodiments of the disclosure is directed to a corrosive environment that is a saline solution. In one embodiment, the saline solution has a pH of at least 2. In yet another embodiment, the saline solution has a pH of at least 4. In another embodiment, the saline solution has a pH of at least 6. In one embodiment, the saline solution has a concentration of NaCl of at least 0.1 g/L. In another embodiment, the saline solution has a concentration of NaCl of at least 0.25 g/L. In yet another embodiment, the saline solution has a concentration of NaCl of at least 1 g/L. In yet another embodiment, the saline solution has a concentration of NaCl of at least 2 g/L. In another embodiment, the saline solution has a concentration of NaCl of at least 5 g/L.

In various embodiments, the disclosure is directed to a surface treatment method for a Ni-based metallic glass comprising immersing at least a portion of a sample of a Ni-based metallic glass in a chemical treatment solution to produce a surface treated portion and removing the surface treated portion from the chemical treatment solution to terminate the chemical surface treatment. In many such embodiments the chemical treatment solution comprises at least one of an acid solution, a chromate solution, and a molybdate solution. After treatment with such embodiments, the Ni ion release rate from the surface treated portion of the sample when immersed in a saline solution for one day is less than 80% of the Ni ion release rate from an as-cast Ni-based metallic glass sample having the same composition similarly immersed in the saline solution for one day.

In another embodiment, the first chemical treatment solution comprises a nitric acid solution.

In another embodiment, the nitric acid concentration in the nitric acid solution is between 5 and 60 volume %.

In another embodiment, the nitric acid concentration in the nitric acid solution is between 20 and 45 volume %.

In another embodiment, the surface treatment method comprises at least two immersion steps. In such embodiments, the method includes (1) immersing at least a portion of the Ni-based metallic glass in a first chemical treatment solution comprising an acid to produce a surface treated portion, and (2) removing the surface treated portion from the first chemical treatment solution.

The method may further include immersing the surface treated portion in a second chemical treatment solution. In many embodiments the second chemical solution comprises at least one of a chromate solution and a molybdenum solution. The surface treated portion is also removed from the second chemical treatment solution.

After treatment, the Ni ion release rate from the surface treated portion when immersed in a saline solution for one day is less than 80% of the Ni ion release rate from an as-cast Ni-based metallic glass sample having the same composition immersed in the saline solution for one day.

In another embodiment, the second chemical treatment solution comprises a sodium dichromate solution.

In another embodiment, the sodium dichromate concentration in the sodium dichromate solution is between 5 and 200 g/L.

In another embodiment, the sodium dichromate concentration in the sodium dichromate solution is between 10 and 100 g/L.

In another embodiment, the second chemical treatment solution comprises a disodium molybdate solution.

In another embodiment, the disodium molybdate concentration in the disodium molybdate solution is between 5 and 200 g/L.

In another embodiment, the disodium molybdate concentration in the disodium molybdate solution is between 10 and 100 g/L.

In one embodiment, the saline solution is a biological solution. In another embodiment, the saline solution is saliva. In another embodiment, the saline solution is perspiration. In another embodiment, the saline solution is blood. In another embodiment, the saline solution is simulated body fluid. In another embodiment, the saline solution is artificial saliva. In another embodiment, the saline solution is artificial perspiration. In another embodiment, the saline solution is artificial blood. In another embodiment, the saline solution is sea water. In another embodiment, the saline solution is simulated sea water.

DEFINITIONS

For the purpose of this disclosure, Ni ion release refers to the mass of extracted Ni ions from a sample exposed to a corrosive environment per surface area of the sample, measured in units of μg/cm².

For the purpose of this disclosure, the Ni ion release rate means the mass of extracted Ni ions from a sample exposed to a corrosive environment per surface area of the sample per day, measured in units of μg/cm²/day.

For the purpose of this disclosure, in some embodiments, a steady-state Ni ion release rate means the Ni ion released rate varies by less than 40% as a function of time in the extraction solution. In other embodiments, a steady-state Ni ion release rate means the Ni ion released rate varies by less than 20% as a function of time in the extraction solution, while in yet other embodiments by less than 10% as a function of time in the extraction solution. In certain embodiments, a steady-state Ni ion release rate means the Ni ion released rate varies by less than 0.1 μg/cm²/day as a function of time in the extraction solution, while in other embodiments by less than 0.06 μg/cm²/day as a function of time in the extraction solution, while in yet other embodiments by less than 0.03 μg/cm²/day as a function of time in the extraction solution.

For the purpose of this disclosure, “as-cast metallic glass” refers to a metallic glass in its as-formed or as-quenched state that has not undergone any chemical surface treatment.

For the purpose of this disclosure, “Ni-based metallic glass” refers to a metallic glass that comprises Ni at an atomic fraction of at least 50%.

For the purpose of this disclosure, the “organic layer” refers to an outermost layer (i.e. the most exterior layer) of the material comprising organic compounds that include elements such as O, C, H and N. The organic layer extends from the outermost surface of the material to a depth into the material where the concentration of Cr peaks. In embodiments of the disclosure, the “organic layer” is not regarded to be an integral part of the “passivated Ni-based metallic glass.”

For the purpose of this disclosure, “passivated Ni-based metallic glass” refers to a Ni-based metallic glass that comprises an inner “bulk material” portion and an outer “passive layer” portion.

For the purpose of this disclosure, the “passive layer” refers to the outer portion of a Ni-based metallic glass (with the organic layer disregarded) that may comprise oxygen in which the atomic concentration of oxygen changes by more than 1% per nanometer of depth into the material (or equivalently, by more than 0.1% per angstrom of depth into the material). In some embodiments, the passive layer may be amorphous (i.e. at least 90% amorphous by volume, or in other embodiments at least 95% amorphous by volume, or in other embodiments at least 98% amorphous by volume). In other embodiments, the passive layer may be crystalline (i.e. more 10% crystalline by volume, or in other embodiments more than 30% crystalline by volume, or in other embodiments more than 50% crystalline by volume).

For the purpose of this disclosure, the “bulk material” refers to the inner portion (the inner bulk material portion) of a Ni-based metallic glass that may comprise oxygen in which the atomic concentration of oxygen changes by less than 1% per nanometer of depth into the material. The inner bulk material portion is substantially amorphous (i.e. at least 90% amorphous by volume, or in other embodiments at least 95% amorphous by volume, or in other embodiments at least 98% amorphous by volume).

For the purpose of this disclosure, the metal moiety of the Ni-based metallic glass refers to the composition of transition metals included in the alloy other than Ni.

For the purpose of this disclosure, the metalloid moiety of the Ni-based metallic glass refers to the composition of metalloids, semimetals, or non-metals included in the alloy.

For the purpose of this disclosure, a Ni-based metallic glass free of Ti refers to a Ni-based metallic glass that contains Ti in an atomic fraction that is equal to or less than the atomic fraction consistent with an incidental impurity. In some embodiments, a Ni-based metallic glass free of Ti refers to a Ni-based metallic glass that contains Ti in an atomic fraction that is equal to or less than 1%. In other embodiments, a Ni-based metallic glass free of Ti refers to a Ni-based metallic glass that contains Ti in an atomic fraction that is equal to or less than 0.5%. In yet other embodiments, a Ni-based metallic glass free of Ti refers to a Ni-based metallic glass that contains Ti in an atomic fraction that is equal to or less than 0.1%.

For the purpose of this disclosure, a saline solution refers to an aqueous solution that comprises at least sodium chloride. In some embodiments, the saline solution is a biological solution, including without limitation saliva, perspiration, and blood plasma. In other embodiments, the saline solution is a physiological solution, including without limitation artificial saliva, artificial perspiration, and artificial blood plasma. In other embodiments, the saline solution is sea water. In yet other embodiments, the saline solution is simulated sea water.

For the purpose of this disclosure, the passive layer of the surface treated sample being poor in Ni refers to a passive layer comprising Ni at a concentration of less than 60 percent of the nominal concentration of Ni in the inner bulk material portion, and in some embodiments less than 40 percent, in other embodiments less than 20 percent, in other embodiments less than 10 percent, while in other embodiments less than 5 percent.

Surface Treatment Process

Many embodiments are directed to a method of chemically surface treating a Ni-based metallic glass comprising at least one immersion step that comprises:

-   -   immersing the Ni-based metallic glass sample in a chemical         treatment solution under specified chemical treatment conditions         to produce a surface treated metallic glass; and     -   removing the surface-treated metallic glass sample from the         chemical treatment solution; where the amount of Ni released by         the surface-treated metallic glass when exposed to a saline         containing environment is lower compared to a metallic glass         that has not undergone any chemical surface treatment

Optionally, the surface-treated metallic glass may be rinsed and dried.

In some embodiments, the chemical treatment solution comprises an acid solution, a chromate solution, a molybdate solution, or a combination thereof.

In some embodiments, the method of chemically surface treating a Ni-based metallic glass involves at least two immersion steps. In one embodiment, at least one step comprises immersion in an acid solution and at least one other step comprises immersion in a chromate solution. In another embodiment, at least one step comprises immersion in an acid solution and at least one other step comprises immersion in a molybdate solution.

For the purpose of this disclosure, immersing the Ni-based metallic glass sample in a chemical treatment solution may comprise exposing one or more portions of the metallic glass sample to the chemical treatment solution under the chemical treatment conditions in order to chemically surface-treat the metallic glass sample.

For the purposes of this disclosure, chemical treatment conditions may include any combination of acid solution a chromate solution, a molybdate solution, or a combination thereof, and also any combination of temperature and immersion time suitable to produce a surface treated metallic glass.

For the purposes of this disclosure, the Ni-ion release rate of the surface treated metallic glass when exposed to a saline containing environment is lower compared to the Ni ion release rate from an as-cast Ni-based metallic glass sample having the same composition exposed to the same saline environment for the same period.

In many embodiments the decrease in the Ni ion release rate for the chemically surface treated Ni-based metallic glass sample when exposed to a saline-containing environment for one day is less than 80% of the Ni ion release rate from an as-cast Ni-based metallic glass sample having the same composition immersed in the same saline solution for the same period.

Any chemical treatment conditions, including immersion time and chemical treatment solution temperature, suitable to produce a surface-treated Ni-based metallic glass sample may be used. In some embodiments, the immersion time is at least 1 min. In one embodiment, the immersion time is at least 10 minutes. In another embodiment, the immersion time is at least 30 minutes. In another embodiment, the immersion time is at least 60 minutes. In yet another embodiment, the immersion time is at least 180 minutes. In yet another embodiment, the immersion time is at least 360 minutes. In some embodiments, the temperature of the chemical treatment solution is at least as high as room temperature. In one embodiment, the temperature of the chemical treatment solution is at least 40° C. In another embodiment, the temperature of the chemical treatment solution is at least 50° C. In yet another embodiment, the temperature of the chemical treatment solution is at least 60° C. In some embodiments, the temperature of the chemical treatment solution is below 100° C. In one embodiment, the temperature of the chemical treatment solution is below 80° C. In another embodiment, the temperature of the chemical treatment solution is below 70° C. In yet another embodiment, the temperature of the chemical treatment solution is below 60° C. The time required for passivation may be temperature dependent with passivation occurring more quickly at higher temperatures. Accordingly, in other embodiments the acid solution temperature may be less than 80° C., and the immersion time may be at least 1 minute.

For the purposes of this disclosure, any suitable method of rinsing and drying the sample as may be known in the art suitable to remove any unwanted residues from the sample prior to working may be utilized.

Surface Treatment of Example Alloys

To demonstrate the effects of the current surface preparation method, the family of Ni—Cr—Nb—P—B—(Si) glass-forming alloys, disclosed in recent applications (U.S. Patent Application No. 61/526,153, entitled “Bulk Nickel-Based Chromium and Phosphorous Bearing Metallic Glasses,” filed on Aug. 22, 2011, and U.S. Patent Application No. 61/720,015, entitled “Bulk Nickel-Based Chromium and Phosphorous Bearing Metallic Glasses with High Toughness,” filed on Oct. 30, 2012), is investigated.

The effect of surface treatment on the Ni-ion release rates of Ni_(71.4)Cr_(5.52)Nb_(3.38)P_(16.67)B_(3.03) metallic glass over an immersion period of up to 15 days in a saline solution is investigated. Two different acid solutions were tested as chemical treatment solutions: a 20 volume % nitric acid, and a 10 weight % citric acid. For both solutions the metallic glass samples were immersed in the chemical treatment solutions at room temperature for 60 minutes. Ni was extracted from the two surface treated samples as well as from an as-cast sample by immersing the samples in a Phosphate Buffered Saline (PBS) solution, which is a simulated body fluid solution whose osmolarity and ion concentrations of the solutions match those of the human body.

The effect of surface treatments in nitric acid and citric acid solutions on the Ni ion release rate of Ni_(71.4)Cr_(5.52)Nb_(3.38)P_(16.67)B_(3.03) metallic glass in Phosphate Buffered Saline solution are shown in FIGS. 1 and 2 respectively. Ni-ion release rate data are provided in Tables 1 and 2. The daily Ni-ion release rates are provided in Table 1, while the weekly Ni-ion release rates are provided in Table 2. The first column in Table 1 lists the total period (in days) that a sample is immersed in solution. The second column lists the period of extraction, that is, the immersion period in a new solution. The third, fourth, and fifth columns list the average daily Ni ion release rate (averaged over the period of extraction) recorded for the as-cast sample, the sample that has undergone surface treatment in nitric acid solution, and the sample that has undergone surface treatment in citric acid solution, respectively. Table 2 provides the weekly Ni-ion release rates observed during the first and second week of immersion.

TABLE 1 Effect of surface treatments in a 20 volume % nitric acid solution and a 10 weight % citric acid solution on the average daily Ni-ion release rate of Ni_(71.4)Cr_(5.52)Nb_(3.38)P_(16.67)B_(3.03) metallic glass in a Phosphate Buffered Saline solution. Total Ni-ion Release Rate (μg/cm²/day) Immersion Extraction Surface-treated Surface-treated Period (days) Period (days) As-cast in Nitric Acid in Citric Acid 1 1 1.000 0.260 0.920 7 6 0.350 0.217 0.283 15 8 0.325 0.238 0.250

TABLE 2 Effect of surface treatments in a 20 volume % nitric acid solution and a 10 weight % citric acid solution on the weekly Ni-ion release rate of Ni_(71.4)Cr_(5.52)Nb_(3.38)P_(16.67)B_(3.03) metallic glass in a Phosphate Buffered Saline solution. Ni-ion Release Rate (μg/cm²/week) Surface-treated in Surface-treated in As-cast Nitric Acid Citric Acid week 1 3.10 1.56 2.62 week 2 2.60 1.90 2.00

The effect of surface treatment on the Ni-ion release rates of Ni_(68.17)Cr_(8.65)Nb_(2.98)P_(16.42)B_(3.28)Si_(0.5) metallic glass over an immersion period of up to 15 days in a saline solution was investigated. A chemical treatment solution comprising a 20 volume % nitric acid solution was used. The metallic glass sample was immersed in the solution at room temperature for 60 minutes. Ni was extracted from the surface treated sample as well as from an as-cast sample by immersing the samples in a Fusayama/Mayer artificial saliva (FAS) solution that resembles the mineral composition of natural saliva and is the most common media used for testing dental metal alloys.

The effect of surface treatment in nitric acid solution on the Ni ion release rate of Ni_(68.17)Cr_(8.65)Nb_(2.98)P_(16.42)B_(3.28)Si_(0.5) metallic glass in a Fusayama/Mayer artificial saliva (FAS) solution is illustrated in FIG. 3 and Tables 3 and 4. The daily Ni-ion release rates are provided in Table 3, while the weekly Ni-ion release rates are provided in Table 4. The first column in Table 3 lists the total period that a sample is immersed in the FAS solution. The second column lists the period of extraction, that is, the immersion period in a new solution. The third and fourth columns list the average daily Ni ion release rate (averaged over the period of extraction) recorded for the untreated as-cast sample, and the sample that has undergone surface treatment in nitric acid solution, respectively. Table 4 provides the weekly Ni-ion release rates observed during the first and second week of immersion.

TABLE 3 Effect of surface treatments in 20 volume % nitric acid solution on the average daily Ni-ion release rate of Ni_(68.17)Cr_(8.65)Nb_(2.98)P_(16.42)B_(3.28)Si_(0.5) metallic glass in a Fusayama/Mayer artificial saliva solution. Total Ni-ion Release Rate (μg/cm²/day) Immersion Extraction Surface-treated in Period (days) Period (days) As-cast Nitric Acid 1 1 0.650 0.082 7 6 0.057 0.028 15 8 0.029 0.014

TABLE 4 Effect of surface treatments in 20 volume % nitric acid solution on the weekly Nickel-ion release rate of Ni_(68.17)Cr_(8.65)Nb_(2.98)P_(16.42)B_(3.28)Si_(0.5) metallic glass in a Fusayama/Mayer artificial saliva solution. Ni-ion Release Rate (μg/cm²/week) Surface-treated in As-cast Nitric Acid week 1 0.99 0.25 week 2 0.23 0.11

As seen in Tables 1 and 3 and FIGS. 1-3, in both PBS and FAS solutions, regardless of the alloy compositions and surface treatments, the average daily Ni release rates are the highest on the first day, and decrease rapidly as a function of time to achieve near steady-state levels after 7 days of immersion.

However, the surface treatment in nitric acid solution decreased the Ni release rates by ˜70-90% for both Ni_(71.4)Cr_(5.52)Nb_(3.38)P_(16.67)B_(3.03) metallic glass in PBS extraction solution, and Ni_(68.17)Cr_(8.65)Nb_(2.98)P_(16.42)B_(3.28)Si_(0.5) in the FAS extraction solution. The Ni-ion release rates in Ni_(71.4)Cr_(5.52)Nb_(3.38)P_(16.67)B_(3.03) that underwent surface-treatment in nitric acid are 0.260 μg/cm²/day on day 1 in simulated body fluid (PBS solution). As a comparison, the Ni release rate in the as-cast untreated material is 1.000 μg/cm²/day, which corresponds to a ˜74% higher Ni release rate (Table 1). In comparison, the Ni-ion release rates in Ni_(68.17)Cr_(8.65)Nb_(2.98)P_(16.42)B_(3.28)S_(0.5) that underwent surface-treatment in nitric acid is 0.082 μg/cm²/day on day 1 in artificial saliva. In contrast, the Ni release rate in the untreated material is 0.650 μg/cm²/day, which corresponds to a ˜87% higher Ni release rate (Table 3).

After 7 days of immersion, the Ni release rates in the untreated as-cast samples of both Ni_(71.4)Cr_(5.52)Nb_(3.38)P_(16.67)B_(3.03) and Ni_(68.17)Cr_(8.65)Nb_(2.98)P_(16.42)B_(3.28)Si_(0.5) decreased significantly by 65% and 91%, respectively, and reached a near steady-state rate. However, the decay in Ni release rates in the Ni_(71.4)Cr_(5.52)Nb_(3.38)P_(16.67)B_(3.03) and Ni_(68.17)Cr_(8.65)Nb_(2.98)P_(16.42)B_(3.28)S_(0.5) samples that have undergone surface-treatment in nitric acid is less significant—16% and 65% after 7 days, respectively. The latter indicates that the nitric acid surface treatment is very effective at creating a stable passive oxide layer and in limiting the bulk of Ni extraction within day 1, thereby enabling the Ni-release process to reach a near steady state in roughly one day. In comparison, the Ni release process in the untreated as-cast Ni alloys takes roughly 7 days to reach a near steady-state.

Similarly, for the first week of immersion, the surface treatment in nitric acid solution decreased the weekly Ni release rates of both Ni_(71.4)Cr_(5.52)Nb_(3.38)P_(16.67)B_(3.03) and Ni_(68.17)Cr_(8.65)Nb_(2.98)P_(16.42)B_(3.28)Si_(0.5) by 50% and 77%, respectively, as compared to the untreated as-cast samples (Tables 2 and 4). On the second week of immersion, the weekly Ni release rates of both surface-treated Ni_(71.4)Cr_(5.52)Nb_(3.38)P_(16.67)B_(3.03) and Ni_(68.17)Cr_(8.65)Nb_(2.98)P_(16.42)B_(3.28)Si_(0.5) has decreased by 27% and 52%, respectively, as compared to the untreated as-cast samples for a similar immersion period.

The Ni release rates in Ni_(68.17)Cr_(8.65)Nb_(2.98)P_(16.42)B_(3.28)Si_(0.5) are significantly lower than in Ni_(71.4)Cr_(5.52)Nb_(3.38)P_(16.67)B_(3.03) in both the samples that have undergone surface-treatment in nitric acid and the untreated as-cast samples throughout the entire immersion period. The difference may be due to the difference in extraction solution—PBS vs FAS media. Another factor may be the difference in the Cr content of the alloys. Ni_(68.17)Cr_(8.65)Nb_(2.98)P_(16.42)B_(3.28)Si_(0.5) has a higher Cr content than Ni_(71.4)Cr_(5.52)Nb_(3.38)P_(16.67)B_(3.03).

On the other hand, the surface treatment in citric acid (FIG. 2) on the Nickel-ion release rate of alloy Ni_(71.4)Cr_(5.52)Nb_(3.38)P_(16.67)B_(3.03) had a less pronounced effect on the Ni leaching. Compared to the Ni release rate of the as-cast untreated sample, the Ni release rate of the sample that has undergone surface-treatment in citric acid decreased by ˜8% from 1.000 to 0.920 μg/cm²/day on day 1. This demonstrates that the citric acid surface treatment, which is commonly used in surface treatments of stainless steel, is not as suitable as nitric acid for providing passivation of Ni-based metallic glasses and reducing Ni release in a saline solution.

In agreement with several studies and as readily accepted by the Food Drug Administration, a threshold Nickel release value of 35 μg/day (Sunderman F W, Jr. “Potential toxicity from nickel contamination of intravenous fluids” Annals of Clinical & Laboratory Science, 1983 13:1-4) is needed to trigger a cytotoxic response. According to the Ni release rates provided in Tables 1 and 3, Ni-based metallic glass samples with composition of Ni_(71.4)Cr_(5.52)Nb_(3.38)P_(16.67)B_(3.03) and Ni_(68.17)Cr_(8.65)Nb_(2.98)P_(16.42)B_(3.28)Si_(0.5), having a surface area up to 134 cm² and 426 cm² respectively, that have undergone a surface treatment according to the methods disclosed herein, would not give rise to Ni toxicity.

Therefore, metallic glass samples that have undergone a surface treatment according to the methods disclosed herein and have a surface area such that the total Ni ion release rate would not exceed 35 μg/day would not give rise to Ni toxicity. In some embodiments, such samples can be used as biomedical components, implants, or devices, including without limitation dental, orthodontic, endodontic, orthopedic, masculofascial, cardiovascular components, implants, or devices.

The effect of surface treatment using chemical treatment solutions comprising a chromate solution on the Ni-ion release rate of Ni_(68.17)Cr_(8.65)Nb_(2.98)P_(16.42)B_(3.28)Si_(0.5) metallic glass over an immersion period of 7 days in a saline solution is investigated. Four different chemical treatment processes using solutions that comprise a chromate solution were performed as follows: (1) a 50 g/L sodium dichromate (Na₂Cr₂O₇) solution, (2) a solution comprising 20 volume % nitric acid combined with 44 g/L sodium dichromate, (3) a solution comprising 40 volume % nitric acid combined with 22 g/L sodium dichromate, (4) and a two-step chemical solution treatment, where the first solution comprises 20 volume % nitric acid combined with 25 g/L sodium dichromate, and the second solution comprises 50 g/L sodium dichromate. In all four chemical treatment processes, the metallic glass samples were immersed in the chemical treatment solutions at 60° C. for 30 minutes. Ni was extracted from the four surface treated samples as well as from an untreated as-polished sample by immersing the samples in an artificial perspiration solution prepared according to standard BS EN1811:2011, which is a simulated perspiration solution whose osmolarity and ion concentrations of the solutions match those of the human skin.

The effect of surface treatments in chemical treatment solutions comprising a chromate solution on the Ni ion release rate of Ni_(68.17)Cr_(8.65)Nb_(2.98)P_(16.42)B_(3.28)Si_(0.5) metallic glass extracted in an artificial perspiration solution are shown in FIG. 4. Table 5 provides the weekly Ni-ion release rates observed during the first week of immersion.

TABLE 5 Effect of surface treatments in chemical treatment solutions comprising a chromate solution on the weekly Ni-ion release rate of Ni_(68.17)Cr_(8.65)Nb_(2.98)P_(16.42)B_(3.28)Si_(0.5) metallic glass extracted in an artificial perspiration solution. Ni-ion Release Rate Passivation Solution (μg/cm²/week) Untreated (as-polished) 1.70 50 g/L Na₂Cr₂O₇ 0.62 20 vol. % HNO₃, 44 g/L Na₂Cr₂O₇ 0.066 40 vol. % HNO₃, 22 g/L Na₂Cr₂O₇ 0.083 Step 1: 20 vol. % HNO₃, 22 g/L Na₂Cr₂O₇ 0.032 Step 2: 50 g/L Na₂Cr₂O₇

As seen in Table 5 and FIG. 4, the most effective surface treatment process in reducing Ni leaching is the a two-step chemical solution treatment with the first solution comprising 20 volume % nitric acid combined with 25 g/L sodium dichromate and the second solution comprises 50 g/L sodium dichromate, as the weekly Ni leach from the treated sample was just 0.032 μg/cm²/week, i.e. about 98% decrease compared to the Ni leach form an untreated sample of 1.7 μg/cm²/week. The second most effective surface treatment process in reducing Ni leaching is treatment in a solution comprising 20 volume % nitric acid combined with 44 g/L sodium dichromate, as the weekly Ni leach from the treated sample was 0.066 μg/cm²/week, i.e. about 96% decrease compared to the Ni leach form an untreated sample of 1.7 μg/cm²/week. The third most effective surface treatment process in reducing Ni leaching is treatment in a solution comprising 40 volume % nitric acid combined with 22 g/L sodium dichromate, as the weekly Ni leach from the treated sample was 0.083 μg/cm²/week, i.e. about 95% decrease compared to the Ni leach form an untreated sample of 1.7 μg/cm²/week. The fourth most effective surface treatment process in reducing Ni leaching is treatment in a solution comprising 50 g/L sodium dichromate, as the weekly Ni leach from the treated sample was 0.62 μg/cm²/week, i.e. about 64% decrease compared to the Ni leach form an untreated sample of 1.7 μg/cm²/week.

To demonstrate the effects of the current surface preparation method, the family of Ni—Mo—Nb—Mn—P—Si glass-forming alloys, disclosed in recent applications (U.S. patent application Ser. No. 14/824,733), is investigated.

The effect of surface treatment using chemical treatment solutions comprising a chromate solution on the Ni-ion release rate of Ni_(73.0)Mo_(2.5)Nb_(3.5)Mn_(1.5)P_(18.0)Si_(1.5) metallic glass over an immersion period of 7 days in a saline solution is investigated. A chemical treatment process using solutions that comprise a chromate solution was performed as follows: a two-step chemical solution treatment, where the first solution comprises 20 volume % nitric acid combined with 25 g/L sodium dichromate, and the second solution comprises 50 g/L sodium dichromate. In this chemical treatment process, the metallic glass sample was immersed in the chemical treatment solutions at 60° C. for 30 minutes. Ni was extracted from the treated sample as well as from an untreated as-polished sample by immersing the samples in an artificial perspiration solution prepared according to standard BS EN1811:2011, which is a simulated perspiration solution whose osmolarity and ion concentrations of the solutions match those of the human skin.

In some embodiments, metallic glass samples that have undergone a surface treatment according to the methods disclosed herein can be used as products or articles that are in contact with the skin over extended periods of time, including without limitation ornamental products (e.g. necklaces or rings), watches, or electronic phones.

Analysis of Surface Chemistry of Example Alloy

The chemical composition and depth profile of the passive layer of as polished (i.e. untreated) and surface treated, according to embodiments of the disclosure, Ni_(68.17)Cr_(8.65)Nb_(2.98)P_(16.42)B_(3.28)Si_(0.5) metallic glass was investigated by XPS/ESCA and SIMS.

An “organic layer” comprising organic compounds that include elements such as O, C, H and N was detected in samples analyzed, having a thickness of less than about 5 angstrom.

In the XPS analysis it is difficult to detect B in the presence of P, because the sole peak of B (B1s) overlaps with one of the P peaks (P2s), and also because XPS is more sensitive to P than B. Hence, in the context of this disclosure, the XPS detection of P may also imply detection of B, and will be denoted as P/B implying detection of P and/or B.

Also, Si was not detected in the XPS analysis, since the atomic concentration of Si in the investigated alloy is very low (0.5%). Hence the concentration distribution of Si in the bulk and surface of the material is not known from this analysis.

Calcium, which is not a constituent or a large impurity of the alloys disclosed herein, was detected on the surface of treated samples as opposed to the as-polished sample, where calcium concentration is negligibly small (<1 at. %). The calcium concentration increases with the concentration of the nitric acid solution. The presence of calcium and the increase in its concentration as the concentration of the nitric acid solution is increased suggest that Ca ions are deposited on the surface from the distilled water used in the dilution of the nitric acid solution.

Table 6 contains XPS sputter depth profile data obtained for an untreated as-polished Ni_(68.17)Cr_(8.65)Nb_(2.98)P_(16.42)B_(3.28)Si_(0.5) metallic glass rod. Data for the composition of the organic layer are not included. The data shows that the surface layer of the untreated as-polished sample comprises 0, P/B, Cr, Nb and Ni (a negligible concentration of Ca was also detected). The thickness of the passive layer (with the organic layer disregarded) is approximately 30 angstrom. The average atomic concentration of O within the passive layer thickness is about 7.2%, that of P/B about 13.1%, that of Cr about 5.5%, that of Nb about 3.0%, and that of Ni about 55.6%. The concentration of P/B is higher in the passive layer than in the inner bulk material portion; the concentration of Cr is approximately the same in the passive layer and inner bulk material portion; while the concentrations of Nb and Ni are lower in the passive layer than in the inner bulk material portion. This suggests that Ni and possibly Nb leach out of the surface into the solution as P/B diffuses from the bulk material to the surface to form the passive layer by combining with O and possibly Cr.

TABLE 6 Atomic concentrations of elements detected by XPS analysis as a function of depth on the surfacef as-polished Ni_(68.17)Cr_(8.65)Nb_(2.98)P_(16.42)B_(3.28)Si_(0.5) metallic glass sample. Element Concentration (in atomic %) Depth (Å) O P/B Cr Nb Ni Ca 0 15.87 14.24 5.88 2.67 53.66 0.83 10 6.76 14.25 5 2.62 67.58 0.32 20 3.47 13.22 5.43 2.99 71.53 0.22 30 2.76 10.54 5.74 3.59 74.8 0.14 45 2.17 8.58 6.46 4.25 75.14 0.19 60 1.84 8.67 6.35 5.19 77.53 0.01 75 1.33 7.81 6.72 5.72 76.17 0 90 1.1 8.72 6.67 5.95 76.17 0 105 1.59 8.33 6.64 6.25 75.69 0 120 0.51 8.68 6.87 6.6 75.53 0 140 0.65 7.9 7.07 6.9 76.28 0 160 0.45 8.53 7.01 7.19 76.29 0 180 0.25 8.67 6.99 7.14 74.76 0

Table 7 contains XPS sputter depth profile data obtained for Ni_(68.17)Cr_(8.65)Nb_(2.98)P_(16.42)B_(3.28)Si_(0.5) metallic glass rods surface treated in a 20 vol. % nitric acid solution for 60 minutes. Data for the composition of the organic layer are not included. The data shows that the passive layers of the surface treated samples comprise O, P/B, Cr, Nb, and Ni (along with a small concentration of Ca). The thickness of the passive layer (with the organic layer disregarded) is approximately 45 angstrom, i.e. about 50% thicker compared to the as-polished sample. The average atomic concentration of O within the passive layer thickness is about 14%, that of P/B about 17.3%, that of Cr about 7.0%, that of Nb about 3.8%, and that of Ni about 55.6%. The concentration of P/B is higher in the passive layer than in the inner bulk material portion; the concentration of Cr is slightly higher in the passive layer than in the inner bulk material portion; while the concentrations of Nb and Ni are lower in the passive layer than in the inner bulk material portion. This suggests that Ni and possibly Nb leaches out of the surface into the solution as P/B and Cr diffuse from the bulk material to the surface to form the passive layer by combining with O. Compared to the as-polished sample, the average concentration of O in the passive layer of the treated sample is about 97% higher, the average concentration of P/B in the passive layer of the treated sample is about 33% higher, the average concentration of Cr in the passive layer of the treated sample is about 27% higher, the average concentration of Nb in the passive layer of the treated sample is about 28% higher, while the average concentration of Ni in the passive layer of the treated sample is about 17% lower.

Hence, in one embodiment, the average concentration of O within the passive layer thickness of a sample of a Ni-based metallic glass comprising Cr and P/B that has been surface treated in a nitric acid solution of concentration of at least 15 vol. % for at least 30 minutes is at least 50% higher when compared to an untreated sample. In another embodiment, the average concentration of P/B within the passive layer thickness of a sample of a Ni-based metallic glass comprising Cr and P/B that has been surface treated in a nitric acid solution of concentration of at least 15 vol. % for at least 30 minutes is at least 20% higher when compared to an untreated sample. In another embodiment, the average concentration of Cr within the passive layer thickness of a sample of a Ni-based metallic glass comprising Cr and P/B that has been surface treated in a nitric acid solution of concentration of at least 15 vol. % for at least 30 minutes is at least 15% higher when compared to an untreated sample. In another embodiment, the average concentration of Ni within the passive layer thickness of a sample of a Ni-based metallic glass comprising Cr and P/B that has been surface treated in a nitric acid solution of concentration of at least 15 vol. % for at least 30 minutes is at least 10% lower when compared to an untreated sample. In other embodiments, the passive layer of a sample of a Ni-based metallic glass comprising Cr and P/B that has been surface treated in a nitric acid solution of concentration of at least 15 vol. % for at least 30 minutes is at least 25% thicker when compared to an untreated sample.

TABLE 7 Atomic concentrations of elements detected by XPS analysis as a function of depth on the surface of polished Ni_(68.17)Cr_(8.65)Nb_(2.98)P_(16.42)B_(3.28)Si_(0.5) metallic glass sample after surface treatment in a 20 vol. % Nitric solution. Element Concentration (in atomic %) Depth (Å) O P/B Cr Nb Ni Ca 0 39.25 18.11 8.78 3.39 25.29 2.61 10 19.01 20 7.17 3.64 48.14 1.41 20 7.26 19.48 5.94 3.34 61.86 0.68 30 3.02 16.35 6.41 4.02 69.66 0.32 45 1.26 12.71 6.63 4.57 73.15 0.26 60 0.66 9.98 7.37 5.69 75.25 0.03 75 0 7.77 7.14 6.05 77.49 0 90 0.38 9.06 6.77 6.63 74.87 0 105 1.08 10.1 7.1 6.77 73.73 0 120 0.55 9.83 6.82 7.43 75.02 0 140 0.43 8.7 6.79 7.55 76.02 0 160 0.39 8.64 7.42 7.74 74.49 0 180 0 9.4 6.88 8 74.66 0

Table 8 contains XPS sputter depth profile data obtained for Ni_(68.17)Cr_(8.65)Nb_(2.98)P_(16.42)B_(3.28)Si_(0.5) metallic glass rods surface treated in a 30 vol. % nitric acid solution for 60 minutes. Data for the composition of the organic layer are not included. The data shows that the passive layers of the surface treated samples comprise O, P/B, Cr, Nb, and Ni (along with a small concentration of Ca). The thickness of the passive layer (with the organic layer disregarded) is approximately 60 angstrom, i.e. about 100% thicker compared to the as-polished sample. The average atomic concentration of O within the passive layer thickness is about 18%, that of P/B about 16.8%, that of Cr about 7.5%, that of Nb about 4.1%, and that of Ni about 50.8%. The concentration of P/B is higher in the passive layer than in the inner bulk material portion; the concentration of Cr is slightly higher in the passive layer than in the inner bulk material portion; while the concentrations of Nb and Ni are lower in the passive layer than in the inner bulk material portion. This suggests that Ni and possibly Nb leach out of the surface into the solution as P/B and Cr diffuse from the bulk material to the surface to form the passive layer by combining with O. Compared to the as-polished sample, the average concentration of 0 in the passive layer of the treated sample is about 150% higher, the average concentration of P/B in the passive layer of the treated sample is about 28% higher, the average concentration of Cr in the passive layer of the treated sample is about 37% higher, the average concentration of Nb in the passive layer of the treated sample is about 39% higher, while the average concentration of Ni in the passive layer of the treated sample is about 24% lower.

Hence, in one embodiment, the average concentration of O within the passive layer thickness of a sample of a Ni-based metallic glass comprising Cr and P/B that has been surface treated in a nitric acid solution of concentration of at least 25 vol. % for at least 30 minutes is at least 75% higher when compared to an untreated sample. In another embodiment, the average concentration of P/B within the passive layer thickness of a sample of a Ni-based metallic glass comprising Cr and P/B that has been surface treated in a nitric acid solution of concentration of at least 25 vol. % for at least 30 minutes is at least 20% higher when compared to an untreated sample. In another embodiment, the average concentration of Cr within the passive layer thickness of a sample of a Ni-based metallic glass comprising Cr and P/B that has been surface treated in a nitric acid solution of concentration of at least 25 vol. % for at least 30 minutes is at least 20% higher when compared to an untreated sample. In another embodiment, the average concentration of Ni within the passive layer thickness of a sample of a Ni-based metallic glass comprising Cr and P/B that has been surface treated in a nitric acid solution of concentration of at least 25 vol. % for at least 30 minutes is at least 15% lower when compared to an untreated sample. In other embodiments, the passive layer of a sample of a Ni-based metallic glass comprising Cr and P/B that has been surface treated in a nitric acid solution of concentration of at least 25 vol. % for 60 minutes is at least 50% thicker when compared to an untreated sample.

TABLE 8 Atomic concentrations of elements detected by XPS analysis as a function of depth on the surface of polished Ni_(68.17)Cr_(8.65)Nb_(2.98)P_(16.42)B_(3.28)Si_(0.5) metallic glass sample after surface treatment in a 30 vol. % Nitric solution. Element Concentration (in atomic %) Depth (Å) O P/B Cr Nb Ni Ca 0 50.8 17.16 8.23 3.62 15.72 3.74 10 32.71 18.55 9.15 3.92 32.36 2.96 20 15.82 19.83 7.56 3.95 49.64 1.56 30 6.01 19.12 6.69 3.89 61.63 0.67 45 2.4 14.34 6.72 4.22 69.93 0.14 60 0.41 11.5 6.94 5.18 75.71 0 75 0.76 9.64 7.07 5.71 74.37 0 90 0.24 9.29 7.51 6.25 75.5 0 105 0.28 8.95 7.36 6.63 74.9 0 120 0.49 8.17 7.13 6.78 75.13 0 140 0.16 8.95 6.84 7.32 75.28 0 160 0.45 9.09 7.28 7.81 74.57 0 180 0.28 7.72 7.83 7.95 76.03 0

Table 9 contains XPS sputter depth profile data obtained for Ni_(68.17)Cr_(8.65)Nb_(2.98)P_(16.42)B_(3.28)Si_(0.5) metallic glass rods surface treated in a 40 vol. % nitric acid solution for 60 minutes. Data for the composition of the organic layer are not included. The data shows that the passive layers of the surface treated samples comprise O, P/B, Cr, Nb, and Ni (along with a small concentration of Ca). The thickness of the passive layer (with the organic layer disregarded) is approximately 90 angstrom, i.e. about 200% thicker compared to the as-polished sample. The average atomic concentration of O within the passive layer thickness is about 29.6%, that of P/B about 16.3%, that of Cr about 8.1%, that of Nb about 4.8%, and that of Ni about 38.1%. The concentration of P/B is higher in the passive layer than in the inner bulk material portion; the concentration of Cr is slightly higher in the passive layer than in the inner bulk material portion; while the concentrations of Nb and Ni are lower in the passive layer than in the inner bulk material portion. This suggests that Ni and possibly Nb leach out of the surface into the solution as P/B and Cr diffuse from the inner bulk material portion to the surface to form the passive layer by combining with O. Compared to the as-polished sample, the average concentration of O in the passive layer of the treated sample is about 310% higher, the average concentration of P/B in the passive layer of the treated sample is about 24% higher, the average concentration of Cr in the passive layer of the treated sample is about 47% higher, the average concentration of Nb in the passive layer of the treated sample is about 61% higher, while the average concentration of Ni in the passive layer of the treated sample is about 43% lower.

Hence, in one embodiment, the average concentration of O within the passive layer thickness of a sample of a Ni-based metallic glass comprising Cr and P/B that has been surface treated in a nitric acid solution of concentration of at least 35 vol. % for at least 30 minutes is at least 100% higher when compared to an untreated sample. In another embodiment, the average concentration of P/B within the passive layer thickness of a sample of a Ni-based metallic glass comprising Cr and P/B that has been surface treated in a nitric acid solution of concentration of at least 35 vol. % for at least 30 minutes is at least 20% higher when compared to an untreated sample. In another embodiment, the average concentration of Cr within the passive layer thickness of a sample of a Ni-based metallic glass comprising Cr and P/B that has been surface treated in a nitric acid solution of concentration of at least 35 vol. % for at least 30 minutes is at least 30% higher when compared to an untreated sample. In another embodiment, the average concentration of Ni within the passive layer thickness of a sample of a Ni-based metallic glass comprising Cr and P/B that has been surface treated in a nitric acid solution of concentration of at least 35 vol. % for at least 30 minutes is at least 25% lower when compared to an untreated sample. In other embodiments, the passive layer of a sample of a Ni-based metallic glass comprising Cr and P/B that has been surface treated in nitric acid solution of concentration of at least 35 vol. % for 60 minutes is at least 100% thicker when compared to an untreated sample.

TABLE 9 Atomic concentrations of elements detected by XPS analysis as a function of depth on the surface of polished Ni_(68.17)Cr_(8.65)Nb_(2.98)P_(16.42)B_(3.28)Si_(0.5) metallic glass sample after surface treatment in a 40 vol. % Nitric solution. Element Concentration (in atomic %) Depth (Å) O P/B Cr Nb Ni Ca 0 64.43 16.26 7.17 3.92 1.98 3.55 10 59.75 17.16 8.37 4.62 5.4 3.8 20 50.99 16.45 9.34 5.17 13.31 3.71 30 37.21 18.52 9.71 5.04 26.75 2.7 45 14.93 19.79 8.17 4.41 50.29 1.17 60 6.09 17.56 7.49 4.31 62.86 0.61 75 2.75 13.39 7.33 5.03 69.69 0.2 90 0.88 10.87 7.34 5.78 74.89 0 105 0.32 10.04 7.75 6.3 74.53 0 120 0.54 9.08 7.58 6.77 74.47 0 140 0.31 9.28 7.18 7.1 73.26 0.19 160 0.67 8.71 7.05 7.47 75.31 0 180 0.57 8.95 7.04 7.55 74.86 0

FIGS. 5-9 provide plots of depth profile up to 200 angstrom for the detected elements by XPS on the surfaces of the as-polished and surface treated samples, including O (FIG. 5), P/B (FIG. 6), Cr (FIG. 7), Nb (FIG. 8), and Ni (FIG. 9), respectively. Data for the composition of the organic layer are not included in the plots.

Table 10 contains SIMS sputter depth profile data up to 60 angstrom in depth obtained for an untreated as-polished Ni_(68.17)Cr_(8.65)Nb_(2.98)P_(16.42)B_(3.28)Si_(0.5) metallic glass rod. Data for the composition of the organic layer are included, but the concentrations of the elements that contribute to the formation of the organic compounds, such as C, H, and N, are not included. The data shows that the organic layer has a thickness of about 4 angstrom (or less than 5 angstrom), and in addition to C, H, and N, the organic layer also comprises primarily O and Si, and is depleted in P, Cr, Nb, B, and Ni. The average atomic concentration of O within the organic layer (within the first 4 angstrom) is about 39.9%, that of Si about 10.7%, that of P about 17.4%, that of Cr about 2.9%, that of Nb about 0.5%, that of B about 0.7%, and that of Ni about 30.2%.

Data for the composition of the surface passive layer, which is the layer immediately adjacent to the organic layer (i.e. extending beyond about 5 angstrom), is presented in Table 11. The composition data suggest that the thickness of the passive layer (excluding the organic layer) is approximately 14 angstrom, and is enriched in O, P, and Cr. The average atomic concentration of O within the passive layer is about 3.9%, that of P about 29.2%, that of Cr about 4.6%, that of Nb about 0.23%, that of B about 0.97%, that of Si about 0.77%, and that of Ni about 60.5%.

The concentration of P is significantly higher in the passive layer than in the inner bulk material portion; the concentrations of Cr, Ni, and Si are approximately the same in the passive layer and inner bulk material portion; while the concentrations of Nb and B are significantly lower in the passive layer than in the inner bulk material portion. This suggests that Nb and B leach out of the surface into the solution as P diffuses from the bulk material to the surface to form the passive layer by combining with O and possibly Cr.

TABLE 10 Atomic concentrations of elements detected by SIMS analysis as a function of depth on the surface of an as-polished (untreated) Ni_(68.17)Cr_(8.65)Nb_(2.98)P_(16.42)B_(3.28)Si_(0.5) metallic glass sample. Element Concentration (in atomic %) Depth (Å) O P Cr Nb B Si Ni 0 32.48 9.59 0.40 1.49 1.36 28.42 19.30 1 53.32 13.67 1.47 0.28 0.50 8.54 26.85 3 45.66 20.20 3.83 0.14 0.43 3.81 32.41 4 28.15 26.30 5.82 0.13 0.36 2.02 42.24 5 14.84 31.19 6.09 0.14 0.35 1.29 49.94 7 8.19 32.97 5.34 0.15 0.39 0.90 53.53 8 5.01 34.01 4.52 0.16 0.45 0.69 55.82 9 3.39 33.17 4.20 0.17 0.53 0.58 57.94 11 2.43 32.22 3.85 0.18 0.69 0.56 59.76 12 1.96 30.96 3.88 0.20 0.85 0.62 61.06 13 1.61 29.28 4.02 0.22 1.06 0.68 62.28 14 1.42 26.67 4.24 0.26 1.26 0.74 64.45 16 1.30 24.97 4.61 0.33 1.47 0.79 65.76 17 1.16 23.31 4.98 0.36 1.66 0.82 67.14 18 1.05 21.92 5.21 0.41 1.86 0.77 68.20 20 0.98 20.88 5.47 0.46 2.03 0.76 68.89 21 0.88 19.63 5.81 0.51 2.12 0.76 70.03 22 0.82 19.27 6.06 0.58 2.24 0.72 70.29 23 0.79 18.80 6.34 0.62 2.36 0.71 70.19 25 0.71 18.32 6.58 0.68 2.45 0.67 70.52 26 0.64 17.87 6.80 0.74 2.53 0.68 70.51 27 0.63 17.05 6.95 0.79 2.57 0.65 71.07 29 0.58 17.57 7.15 0.86 2.66 0.67 71.01 30 0.50 17.63 7.35 0.91 2.69 0.64 70.27 31 0.51 17.01 7.36 1.00 2.70 0.60 70.49 33 0.47 16.82 7.48 0.99 2.75 0.58 71.08 34 0.44 16.72 7.76 1.07 2.84 0.60 70.52 35 0.40 16.99 7.89 1.16 2.81 0.58 70.42 36 0.37 16.94 7.80 1.22 2.84 0.55 70.19 38 0.37 16.88 7.88 1.24 2.91 0.61 70.17 39 0.33 16.77 7.94 1.28 2.87 0.59 70.19 40 0.32 16.45 8.23 1.34 2.89 0.55 70.26 42 0.28 16.43 8.18 1.43 2.97 0.53 70.19 43 0.27 16.72 8.25 1.49 3.00 0.58 69.83 44 0.27 16.58 8.29 1.57 3.06 0.60 69.59 45 0.24 16.62 8.29 1.58 3.02 0.54 69.77 47 0.23 16.68 8.35 1.63 3.09 0.61 69.52 48 0.22 16.75 8.37 1.66 3.08 0.54 69.44 49 0.20 16.60 8.47 1.66 3.10 0.55 69.30 51 0.18 16.40 8.45 1.72 3.06 0.55 69.49 52 0.19 16.36 8.47 1.79 3.10 0.57 69.76 53 0.19 15.17 8.52 1.77 2.88 0.56 69.21 54 0.16 15.47 7.75 1.79 3.05 0.48 72.82 56 0.16 16.35 8.50 1.96 3.16 0.55 69.20 57 0.16 16.40 8.66 1.95 3.17 0.51 69.35 58 0.14 16.51 8.82 2.02 3.20 0.53 68.77 60 0.14 16.62 8.58 2.03 3.25 0.53 68.99

Table 11 contains SIMS sputter depth profile data obtained for Ni_(68.17)Cr_(8.65)Nb_(2.98)P_(16.42)B_(3.28)Si_(0.5) metallic glass rods surface treated in a 20 vol. % nitric acid solution for 60 minutes. Data for the composition of the organic layer are included, but the concentrations of the elements that contribute to the formation of the organic compounds, such as C, H, and N, are not included. The data shows that the organic layer has a thickness of about 4 angstrom (or less than 5 angstrom), and in addition to C, H, and N, the organic layer is rich in O, Si, and P, and is depleted in Cr, Nb, B, and Ni. The average atomic concentration of O within the organic layer thickness (within the first 4 angstrom) is about 49.1%, that of Si about 7.1%, that of P about 24.8%, that of Cr about 3.3%, that of Nb about 0.15%, that of B about 0.5%, and that of Ni about 16.3%.

Data for the composition of the passive layer, which is the layer immediately adjacent to the organic layer (i.e. extending beyond about 5 angstrom), is presented in Table 10. The composition data suggest that the thickness of the passive layer (excluding the organic layer) is approximately 14 angstrom, and is enriched in O and P and poor in Nb and B. The average atomic concentration of O within the passive layer thickness is about 4.6%, that of P about 35.3%, that of Cr about 5.8%, that of Nb about 0.3%, that of B about 0.94%, that of Si about 0.54%, and that of Ni about 52.8%.

The concentration of P is significantly higher in the passive layer than in the inner bulk material portion; the concentration of Si is approximately the same in the passive layer as in the inner bulk material portion; the concentrations of Cr and Ni are slightly lower in the passive layer than in the inner bulk material portion; while the concentrations of B and Nb are significantly lower in the passive layer than in the inner bulk material portion. This suggests that Nb and B and possibly Ni and Cr leach out of the surface into the solution as P diffuses from the bulk material to the surface to form the passive layer by combining with O and possibly Cr.

Compared to the passive layer of the as-polished sample, the average concentration of O in the passive layer of the treated sample is about 19% higher, the average concentration of P in the passive layer of the treated sample is about 21% higher, the average concentration of Cr in the passive layer of the treated sample is about 25% higher, the average concentration of Nb in the passive layer of the treated sample is about 30% higher, the average concentration of B in the passive layer of the treated sample is about 3% lower, the average concentration of Si in the passive layer of the treated sample is about 30% lower, while the average concentration of Ni in the passive layer of the treated sample is about 12% lower.

Hence, in one embodiment, the average concentration of O within the passive layer thickness of a sample of a Ni-based metallic glass comprising Cr and P that has been surface treated in a nitric acid solution of concentration of at least 15 vol. % for at least 30 minutes is at least 5% higher when compared to an untreated sample. In another embodiment, the average concentration of P within the passive layer thickness of a sample of a Ni-based metallic glass comprising Cr and P that has been surface treated in a nitric acid solution of concentration of at least 15 vol. % for at least 30 minutes is at least 10% higher when compared to an untreated sample. In another embodiment, the average concentration of Cr within the passive layer thickness of a sample of a Ni-based metallic glass comprising Cr and P that has been surface treated in a nitric acid solution of concentration of at least 15 vol. % for at least 30 minutes is at least 15% higher when compared to an untreated sample. In another embodiment, the average concentration of Ni within the passive layer thickness of a sample of a Ni-based metallic glass comprising Cr and P that has been surface treated in a nitric acid solution of concentration of at least 15 vol. % for at least 30 minutes is at least 5% lower when compared to an untreated sample.

TABLE 11 Atomic concentrations of elements detected by SIMS analysis as a function of depth on the surface of polished Ni_(68.17)Cr_(8.65)Nb_(2.98)P_(16.42)B_(3.28)Si_(0.5) metallic glass sample after surface treatment in a 20 vol. % nitric acid solution. Element Concentration (in atomic %) Depth (Å) O P Cr Nb B Si Ni 0 39.09 17.84 0.70 0.31 0.81 22.18 8.10 1 68.22 21.91 1.79 0.08 0.37 3.57 9.26 3 54.81 27.01 4.27 0.10 0.41 1.65 17.60 4 34.11 32.34 6.56 0.12 0.41 1.08 30.23 5 19.12 35.98 7.28 0.16 0.43 0.85 39.58 7 10.59 37.57 6.81 0.19 0.47 0.59 45.51 8 6.41 38.13 6.06 0.22 0.48 0.48 48.92 9 4.02 38.02 5.55 0.25 0.56 0.42 51.45 11 2.82 37.85 5.24 0.26 0.66 0.35 52.94 12 2.11 37.64 5.04 0.27 0.77 0.39 53.80 13 1.64 36.04 5.15 0.31 0.93 0.43 54.83 14 1.31 34.41 5.26 0.34 1.11 0.51 56.30 16 1.10 32.59 5.43 0.39 1.36 0.55 58.14 17 0.94 30.77 5.65 0.43 1.68 0.66 59.02 18 0.76 28.86 5.91 0.48 1.90 0.67 60.60 20 0.72 26.50 6.17 0.52 2.16 0.72 62.27 21 0.65 25.19 6.47 0.56 2.42 0.72 63.66 22 0.56 23.76 6.90 0.65 2.58 0.73 64.21 23 0.53 22.63 6.99 0.70 2.73 0.69 65.18 25 0.44 21.40 7.16 0.78 2.87 0.74 66.13 26 0.40 20.85 7.47 0.82 2.99 0.73 66.65 27 0.40 20.23 7.65 0.93 3.09 0.67 66.97 29 0.35 19.61 7.91 0.96 3.21 0.63 67.08 30 0.32 19.26 7.97 1.03 3.23 0.60 67.36 31 0.32 18.46 8.00 1.08 3.28 0.62 67.85 33 0.25 18.22 8.29 1.10 3.27 0.58 68.37 34 0.25 18.25 8.39 1.28 3.42 0.53 68.08 35 0.24 18.30 8.36 1.26 3.43 0.54 67.88 36 0.21 17.79 8.49 1.34 3.46 0.57 67.75 38 0.21 17.61 8.58 1.33 3.43 0.56 68.30 39 0.19 17.57 8.70 1.45 3.43 0.56 68.28 40 0.18 17.69 8.74 1.52 3.54 0.55 67.73 42 0.16 17.29 8.84 1.59 3.58 0.55 67.91 43 0.15 16.93 8.75 1.63 3.55 0.56 68.22 44 0.14 17.02 8.95 1.62 3.46 0.51 68.39 45 0.13 17.25 9.04 1.77 3.53 0.54 67.95 47 0.12 17.20 8.85 1.74 3.56 0.51 67.97 48 0.13 16.82 8.82 1.72 3.60 0.50 68.12 49 0.13 17.06 8.94 1.79 3.55 0.57 68.17 51 0.11 17.01 8.83 1.87 3.55 0.50 68.25 52 0.12 17.29 8.81 1.98 3.70 0.53 67.80 53 0.11 17.23 8.96 1.94 3.71 0.52 67.42 54 0.12 17.04 8.92 1.98 3.62 0.51 67.66 56 0.09 16.76 8.98 2.01 3.56 0.54 68.01 57 0.08 17.15 9.05 2.09 3.62 0.50 67.80 58 0.09 17.11 8.99 2.15 3.65 0.51 67.53 60 0.09 16.83 8.93 2.16 3.70 0.52 67.49

FIGS. 10-16 provide plots of depth profile up to 200 angstrom for the detected elements by SIMS on the surfaces of the as-polished and surface treated samples, including O (FIG. 10), P (FIG. 11), Cr (FIG. 12), Nb (FIG. 13), B (FIG. 14), Si (FIG. 15), and Ni (FIG. 16), respectively. The insets provide plots of depth profile up to 60 angstrom for the detected elements, and the regions for the “organic layer,” “passive layer,” and “bulk material” are designated by arrows.

The depth profiles indicate the samples have a general profile comprising a passive layer that has thickness in the range of 10 to 100 angstrom, with the thickness increasing with increasing the concentration of the nitric acid solution. The inner bulk material portion of the metallic glass alloy is located underneath the passive layer.

Table 12 contains SIMS sputter depth profile data obtained for Ni_(68.17)Cr_(8.65)Nb_(2.98)P_(16.42)B_(3.28)Si_(0.5) metallic glass rods surface treated in 50 g/L sodium dichromate at 60° C. for 30 minutes. Data for the composition of the organic outermost layer are included, but the concentrations of the elements that contribute to the formation of the organic compounds, such as C, H, and N, are not included. The data shows that the organic layer has a thickness of about 8 angstrom (or less than 9 angstrom), and in addition to C, H, and N, the organic layer is also rich in O and Si and is depleted in Cr, Nb, B, and Ni. The average atomic concentration of O within the organic layer thickness (within the first 8 angstrom) is about 64.1%, that of Si about 4.5%, that of P about 14.1%, that of Cr about 3.5%, that of Nb about 0.21%, that of B about 0.45%, and that of Ni about 15.1%.

Data for the composition of the passive layer, which is the layer immediately adjacent to the organic layer (i.e. extending beyond about 8 angstrom), is presented in Table 11. The composition data suggest that the thickness of the passive layer (excluding the organic layer) is approximately 63 angstrom, and is rich in O and P and poor in Nb and B. The average atomic concentration of O within the passive layer thickness is about 8.5%, that of P about 22.6%, that of Cr about 4.8%, that of Nb about 0.45%, that of B about 1.6%, that of Si about 0.72%, and that of Ni about 61.4%.

Compared to the passive layer of the as-polished sample, whose thickness is about 13 angstrom, the passive layer thickness of the treated sample is about 385% thicker. Hence, in one embodiment, the passive layer of a sample that has been surface treated in a sodium dichromate solution having concentration of at least 25 g/L at temperature of at least 45° C. for at least 15 minutes is at least 50% thicker than the passive layer of an untreated sample. In another embodiment, the passive layer of a sample of a sample that has been surface treated in a sodium dichromate solution having concentration of at least 25 g/L at temperature of at least 45° C. for at least 15 minutes is at least 100% thicker than the passive layer of an untreated sample. In another embodiment, the passive layer of a sample that has been surface treated in a sodium dichromate solution having concentration of at least 25 g/L at temperature of at least 45° C. for at least 15 minutes is at least 200% thicker than the passive layer of an untreated sample. In yet another embodiment, the passive layer of a sample that has been surface treated in a sodium dichromate solution having concentration of at least 25 g/L at temperature of at least 45° C. for at least 15 minutes is at least 300% thicker than the passive layer of an untreated sample.

TABLE 12 Atomic concentrations of elements detected by SIMS analysis as a function of depth on the surface of polished Ni_(68.17)Cr_(8.65)Nb_(2.98)P_(16.42)B_(3.28)Si_(0.5) metallic glass sample after surface treatment in a 50 g/L sodium dichromate solution. Element Concentration (in atomic %) Depth (Å) O P Cr Nb B Si Ni 0 64.09 7.76 1.83 0.56 0.84 12.72 8.34 2 73.65 11.35 2.98 0.14 0.35 2.40 10.87 5 66.62 15.36 4.03 0.08 0.28 1.64 16.20 7 51.86 22.05 5.18 0.06 0.25 1.31 25.01 9 34.91 26.33 5.27 0.04 0.25 1.09 35.67 11 24.57 29.19 4.45 0.05 0.30 0.90 43.04 14 18.89 29.86 3.74 0.06 0.36 0.75 47.50 16 15.54 29.77 3.32 0.07 0.49 0.73 50.36 18 14.00 28.08 3.17 0.09 0.62 0.73 52.73 20 13.04 25.86 3.18 0.10 0.79 0.73 55.37 22 12.14 24.45 3.29 0.13 0.95 0.80 57.90 25 11.12 23.37 3.46 0.15 1.06 0.77 59.78 27 10.34 22.72 3.69 0.19 1.23 0.77 60.94 29 9.56 22.34 3.81 0.22 1.33 0.74 61.94 31 8.73 21.79 4.04 0.24 1.38 0.73 63.12 34 8.05 21.58 4.26 0.27 1.50 0.71 63.72 36 7.37 21.95 4.42 0.31 1.57 0.69 64.05 38 6.76 22.00 4.54 0.35 1.72 0.72 64.13 40 6.14 21.55 4.73 0.40 1.78 0.69 64.57 42 5.54 21.40 4.85 0.42 1.84 0.70 65.41 45 5.08 21.33 5.09 0.46 1.91 0.67 65.58 47 4.69 21.36 5.19 0.52 2.01 0.67 65.82 49 4.12 21.40 5.32 0.58 2.13 0.69 65.82 51 3.86 20.74 5.46 0.61 2.16 0.71 66.31 54 3.56 20.72 5.57 0.66 2.19 0.69 66.66 56 3.22 20.62 5.75 0.71 2.27 0.70 66.86 58 2.99 20.42 5.78 0.76 2.37 0.65 66.92 60 2.71 20.08 5.93 0.80 2.40 0.68 67.41 62 2.49 19.39 6.02 0.84 2.45 0.68 67.86 65 2.30 19.53 6.14 0.91 2.50 0.67 68.21 67 2.10 19.64 6.23 0.98 2.58 0.67 67.89 69 2.00 19.61 6.29 1.00 2.63 0.64 67.87 71 1.80 19.04 6.34 1.05 2.69 0.64 68.15 74 1.72 18.84 6.48 1.08 2.66 0.66 68.57 76 1.61 18.90 6.49 1.14 2.73 0.64 68.67 78 1.49 18.93 6.57 1.19 2.79 0.64 68.44 80 1.41 18.54 6.64 1.26 2.78 0.66 68.48 82 1.35 18.43 6.69 1.28 2.80 0.62 68.79 85 1.25 18.27 6.78 1.30 2.80 0.63 69.06 87 1.16 18.26 6.87 1.38 2.90 0.65 68.78 89 1.11 18.22 6.95 1.44 2.91 0.65 68.73 91 1.08 17.77 6.87 1.44 2.88 0.64 69.10 94 0.99 17.68 7.00 1.46 2.88 0.62 69.39 96 0.92 17.87 7.06 1.57 2.93 0.64 69.22 98 0.89 18.04 7.04 1.58 2.96 0.64 68.91 100 0.84 17.60 7.09 1.58 2.97 0.64 69.02 102 0.81 17.43 7.17 1.63 2.97 0.64 69.31 105 0.77 17.46 7.23 1.67 2.97 0.64 69.37 107 0.73 17.78 7.26 1.73 3.00 0.63 69.08 109 0.72 17.53 7.31 1.75 3.08 0.64 68.89 111 0.69 17.33 7.32 1.78 3.05 0.64 69.01 114 0.62 17.28 7.27 1.79 3.03 0.63 69.41 116 0.63 17.43 7.40 1.87 3.07 0.63 69.14 118 0.60 17.47 7.47 1.90 3.13 0.63 68.93 120 0.59 17.33 7.38 1.89 3.06 0.63 68.82 123 0.55 16.91 7.41 1.89 3.07 0.61 69.50 125 0.57 17.03 7.55 1.97 3.07 0.62 69.33 127 0.54 17.11 7.61 2.01 3.09 0.64 69.06 129 0.48 17.09 7.52 2.03 3.13 0.61 69.10 131 0.49 17.14 7.58 2.04 3.13 0.63 69.00 134 0.48 16.93 7.65 2.02 3.07 0.61 69.17 136 0.48 17.04 7.73 2.09 3.10 0.63 69.08 138 0.45 17.24 7.68 2.10 3.18 0.60 68.80 140 0.43 17.34 7.68 2.14 3.16 0.65 68.67 143 0.43 16.87 7.68 2.11 3.15 0.63 68.84 145 0.42 16.75 7.77 2.19 3.12 0.62 69.17 147 0.39 17.15 7.82 2.16 3.14 0.62 68.96 149 0.41 16.99 7.76 2.24 3.18 0.59 68.75 151 0.39 16.83 7.85 2.23 3.19 0.61 68.76 154 0.39 16.71 7.83 2.22 3.14 0.63 69.02 156 0.36 16.92 7.93 2.26 3.14 0.61 68.99 158 0.36 17.02 7.97 2.32 3.19 0.62 68.56 160 0.34 16.97 7.90 2.32 3.16 0.62 68.61 163 0.34 16.72 7.80 2.34 3.13 0.61 68.96 165 0.34 16.68 8.00 2.32 3.14 0.62 69.00 167 0.33 16.86 8.06 2.37 3.17 0.59 68.67 169 0.31 17.09 7.94 2.36 3.20 0.64 68.56 171 0.31 16.76 7.98 2.39 3.19 0.60 68.54 174 0.29 16.45 8.09 2.39 3.17 0.65 68.93 176 0.30 16.48 8.07 2.46 3.16 0.61 68.90 178 0.30 16.87 8.05 2.47 3.21 0.63 68.78 180 0.28 16.92 8.04 2.47 3.24 0.61 68.44 183 0.27 16.91 8.05 2.42 3.23 0.61 68.36 185 0.28 16.65 8.08 2.41 3.18 0.63 68.72 187 0.27 16.77 8.12 2.50 3.23 0.59 68.72 189 0.27 16.69 8.19 2.51 3.26 0.58 68.43 191 0.24 16.69 8.11 2.48 3.24 0.61 68.50 194 0.22 16.64 8.08 2.44 3.16 0.63 68.82 196 0.23 16.40 8.22 2.49 3.18 0.56 68.89 198 0.22 16.92 8.22 2.53 3.28 0.62 68.54 200 0.23 16.77 8.26 2.55 3.26 0.59 68.16 203 0.23 16.75 8.13 2.52 3.22 0.59 68.59 205 0.21 16.82 8.20 2.54 3.21 0.62 68.44 207 0.21 16.54 8.30 2.62 3.20 0.61 68.40 209 0.21 16.76 8.28 2.63 3.30 0.58 68.45 212 0.21 16.62 8.24 2.58 3.29 0.58 68.29 214 0.20 16.56 8.26 2.60 3.25 0.61 68.46 216 0.22 16.50 8.32 2.62 3.23 0.63 68.49 218 0.20 16.51 8.29 2.59 3.23 0.60 68.63 220 0.18 16.79 8.31 2.63 3.29 0.60 68.34 223 0.20 16.60 8.25 2.65 3.22 0.60 68.31 225 0.18 16.48 8.28 2.59 3.24 0.61 68.55 227 0.18 16.33 8.33 2.60 3.24 0.59 68.78 229 0.18 16.51 8.44 2.66 3.30 0.60 68.37 232 0.18 16.76 8.33 2.64 3.26 0.60 68.28 234 0.19 16.27 8.23 2.63 3.24 0.60 68.62 236 0.16 16.53 8.41 2.64 3.22 0.62 68.60 238 0.17 16.56 8.38 2.65 3.25 0.58 68.48 240 0.17 16.62 8.44 2.74 3.28 0.61 68.17 243 0.17 16.73 8.34 2.70 3.27 0.60 68.16 245 0.16 16.59 8.39 2.72 3.25 0.61 68.27 247 0.16 16.58 8.37 2.70 3.26 0.59 68.40 249 0.16 16.88 8.42 2.74 3.24 0.60 68.04 252 0.17 16.72 8.36 2.70 3.33 0.56 68.14 254 0.14 16.38 8.40 2.67 3.27 0.59 68.27 256 0.15 16.29 8.43 2.68 3.25 0.61 68.61 258 0.14 16.68 8.46 2.71 3.22 0.61 68.39 260 0.14 16.78 8.45 2.71 3.25 0.61 68.11 263 0.14 16.36 8.37 2.75 3.26 0.59 68.29 265 0.13 16.53 8.39 2.72 3.23 0.61 68.52 267 0.13 16.49 8.52 2.71 3.20 0.58 68.31 269 0.14 16.69 8.48 2.71 3.24 0.57 68.34 272 0.13 16.62 8.42 2.77 3.27 0.56 68.09 274 0.13 16.51 8.38 2.75 3.31 0.59 68.42 276 0.13 16.36 8.45 2.75 3.24 0.58 68.32 278 0.12 16.61 8.59 2.78 3.27 0.60 68.27 280 0.13 16.73 8.44 2.79 3.29 0.61 67.98 283 0.12 16.48 8.44 2.74 3.34 0.58 68.19 285 0.12 16.33 8.40 2.79 3.29 0.59 68.40 287 0.12 16.43 8.54 2.74 3.25 0.58 68.43 289 0.11 16.64 8.48 2.79 3.30 0.58 68.19 292 0.11 16.47 8.51 2.80 3.29 0.58 68.22 294 0.11 16.56 8.51 2.74 3.28 0.61 68.05 296 0.12 16.28 8.51 2.78 3.29 0.60 68.51 298 0.11 16.34 8.58 2.80 3.25 0.56 68.25 300 0.11 16.83 8.48 2.83 3.26 0.57 68.22 303 0.11 16.55 8.49 2.82 3.29 0.58 67.98 305 0.11 16.49 8.45 2.76 3.31 0.58 68.32 307 0.11 16.29 8.53 2.79 3.26 0.57 68.33 309 0.10 16.62 8.61 2.82 3.32 0.58 68.25 312 0.10 16.65 8.54 2.84 3.32 0.54 67.93 314 0.09 16.52 8.53 2.89 3.32 0.58 67.92 316 0.09 16.18 8.44 2.77 3.26 0.58 68.53 318 0.09 16.50 8.51 2.85 3.26 0.57 68.47 321 0.10 16.42 8.56 2.85 3.32 0.59 68.15 323 0.09 16.47 8.53 2.81 3.30 0.58 68.11 325 0.09 16.31 8.47 2.85 3.25 0.59 68.39 327 0.09 16.21 8.61 2.80 3.25 0.58 68.41 329 0.10 16.42 8.62 2.86 3.26 0.59 68.36 332 0.09 16.55 8.52 2.85 3.32 0.58 68.15 334 0.09 16.55 8.51 2.82 3.29 0.54 68.05 336 0.08 16.31 8.52 2.81 3.26 0.56 68.40 338 0.09 16.50 8.60 2.82 3.26 0.57 68.34 341 0.09 16.70 8.64 2.87 3.30 0.59 67.84 343 0.08 16.50 8.59 2.89 3.29 0.57 68.04 345 0.08 16.41 8.58 2.84 3.34 0.55 68.02 347 0.08 16.59 8.59 2.87 3.23 0.58 68.21 349 0.07 16.41 8.59 2.86 3.30 0.56 68.21

FIGS. 17-23 provide plots of depth profiles up to 350 angstrom for the detected elements by SIMS on the surfaces of the as-polished sample and the sample surface treated in a 50 g/L sodium dichromate solution, including O (FIG. 17), P (FIG. 18), Cr (FIG. 19), Nb (FIG. 20), B (FIG. 21), Si (FIG. 22), and Ni (FIG. 23), respectively. The insets provide plots of depth profiles up to 100 angstrom for the detected elements, and the regions for the “organic layer,” “passive layer,” and “bulk material” are designated by arrows.

Table 13 contains SIMS sputter depth profile data obtained for Ni_(68.17)Cr_(8.65)Nb_(2.98)P_(16.42)B_(3.28)Si_(0.5) metallic glass rods surface treated by a two-step chemical solution treatment (the first solution comprises 20 volume % nitric acid combined with 25 g/L sodium dichromate, and the second solution comprises 50 g/L sodium dichromate) at 60° C. for 30 minutes in each step. Data for the composition of the organic outermost layer are included, but the concentrations of the elements that contribute to the formation of the organic compounds, such as C, H, and N, are not included. The data shows that the organic layer has a thickness of about 8 angstrom (or less than 9 angstrom), and in addition to C, H, and N, the organic layer is also rich in O and Si and is depleted in Cr, Nb, B, and Ni. The average atomic concentration of O within the organic layer thickness (within the first 8 angstrom) is about 54.8%, that of Si about 10.6%, that of P about 16.2%, that of Cr about 5.6%, that of Nb about 0.21%, that of B about 0.63%, and that of Ni about 15.1%.

Data for the composition of the passive layer, which is the layer immediately adjacent to the organic layer (i.e. extending beyond about 8 angstrom), is presented in Table 11. The composition data suggest that the thickness of the passive layer (excluding the organic layer) is approximately 12 angstrom, and is rich in O and P and poor in Ni, Nb and B. The average atomic concentration of O within the passive layer thickness is about 1.45%, that of P about 31.7%, that of Cr about 6.2%, that of Nb about 0.31%, that of B about 1.2%, that of Si about 0.51%, and that of Ni about 57.7%.

The concentration of P is significantly higher in the passive layer than in the inner bulk material portion; the concentration of Si is approximately the same in the passive layer as in the inner bulk material portion; the concentration of Cr is slightly lower in the passive layer than in the inner bulk material portion; while the concentrations of Ni, B and Nb are significantly lower in the passive layer than in the inner bulk material portion. This suggests that Nb and B and possibly Ni and Cr leach out of the surface into the solution as P diffuses from the bulk material to the surface to form the passive layer by combining with O and possibly Cr.

Compared to the passive layer of the as-polished sample, the average concentration of O in the passive layer of the treated sample is about 63% lower, the average concentration of P in the passive layer of the treated sample is about 9% higher, the average concentration of Cr in the passive layer of the treated sample is about 34% higher, the average concentration of Nb in the passive layer of the treated sample is about 36% lower, the average concentration of B in the passive layer of the treated sample is about 23% lower, the average concentration of Si in the passive layer of the treated sample is about 34% lower, while the average concentration of Ni in the passive layer of the treated sample is about 5% lower.

Hence, in one embodiment, the average concentration of P within the passive layer thickness of a sample of a Ni-based metallic glass comprising Cr and P that has been surface treated by a two-step chemical solution treatment, where the first solution comprises nitric acid combined with odium dichromate, and the second solution comprises sodium dichromate, for at least 15 minutes is at least 5% higher when compared to an untreated sample. In another embodiment, the average concentration of Cr within the passive layer thickness of a sample of a Ni-based metallic glass comprising Cr and P that has been surface treated by a two-step chemical solution treatment, where the first solution comprises nitric acid combined with odium dichromate, and the second solution comprises sodium dichromate, for at least 15 minutes is at least 25% higher when compared to an untreated sample. In another embodiment, the average concentration of Ni within the passive layer thickness of a sample of a Ni-based metallic glass comprising Cr and P that has been surface treated by a two-step chemical solution treatment, where the first solution comprises nitric acid combined with odium dichromate, and the second solution comprises sodium dichromate, for at least 15 minutes is at least 2% lower when compared to an untreated sample.

TABLE 13 Atomic concentrations of elements detected by SIMS analysis as a function of depth on the surface of polished Ni_(68.17)Cr_(8.65)Nb_(2.98)P_(16.42)B_(3.28)Si_(0.5) metallic glass sample surface treated by a two-step chemical solution treatment (the first solution comprises 20 volume % nitric acid combined with 25 g/L sodium dichromate, and the second solution comprises 50 g/L sodium dichromate). Element Concentration (in atomic %) Depth (Å) O P Cr Nb B Si Ni 0 39.06 5.83 1.30 0.49 1.11 38.72 8.07 2 75.87 12.18 3.81 0.11 0.50 1.89 12.03 5 64.67 18.87 6.60 0.11 0.50 1.10 13.36 7 39.65 28.11 10.79 0.13 0.41 0.88 26.10 9 16.44 34.48 11.08 0.17 0.40 0.58 41.26 11 6.25 36.87 8.65 0.19 0.45 0.38 49.33 14 2.67 36.71 6.68 0.23 0.64 0.33 53.18 16 1.41 34.34 5.82 0.26 0.94 0.39 55.91 18 0.98 30.03 5.84 0.33 1.39 0.57 59.23 20 0.72 25.71 6.29 0.43 1.81 0.73 62.54 22 0.59 22.75 6.85 0.55 2.20 0.78 65.09 25 0.47 20.54 7.19 0.67 2.50 0.74 67.11 27 0.41 19.03 7.56 0.76 2.63 0.73 68.19 29 0.37 17.99 7.86 0.90 2.70 0.64 69.27 31 0.30 17.62 8.25 1.00 2.85 0.64 69.32 34 0.27 17.19 8.38 1.11 2.92 0.61 69.47 36 0.23 17.21 8.45 1.21 2.99 0.59 69.38 38 0.22 16.87 8.59 1.31 3.01 0.57 69.27 40 0.19 16.66 8.71 1.37 2.99 0.60 69.48 42 0.18 16.72 8.77 1.52 3.02 0.53 69.47 45 0.17 16.70 8.75 1.65 3.08 0.57 69.02 47 0.14 16.80 8.80 1.70 3.09 0.55 69.06 49 0.13 16.55 8.77 1.76 3.06 0.55 69.00 51 0.13 16.42 8.86 1.90 3.10 0.54 69.19 54 0.12 16.76 8.89 1.93 3.11 0.55 68.75 56 0.11 16.84 8.81 2.01 3.13 0.53 68.65 58 0.11 16.38 8.79 2.07 3.15 0.56 68.67 60 0.11 16.35 8.87 2.14 3.10 0.55 68.93

FIGS. 24-30 provide plots of depth profiles up to 200 angstrom for the detected elements by SIMS on the surfaces of the as-polished sample and the sample surface treated by a two-step chemical solution treatment (where the first solution comprises 20 volume % nitric acid combined with 25 g/L sodium dichromate, and the second solution comprises 50 g/L sodium dichromate), including O (FIG. 24), P (FIG. 25), Cr (FIG. 26), Nb (FIG. 27), B (FIG. 28), Si (FIG. 29), and Ni (FIG. 30), respectively. The insets provide plots of depth profile up to 60 angstrom for the detected elements, and the regions for the “organic layer” of each sample are designated by arrows.

The data in Tables 5, 10, 12, and 13 suggest that the higher the average Cr concentration in the passive layer, the lower the Ni ion release rate in a given solution (artificial perspiration in the present case). The average Cr concentration in the passive layer of untreated Ni_(68.17)Cr_(8.65)Nb_(2.98)P_(16.42)B_(3.28)Si_(0.5) metallic glass is 4.6% (analysis of Table 10), while the Ni-ion release rate during exposure of these rods to an artificial perspiration solution is 1.7 μg/cm²/week (Table 5). The average Cr concentration in the passive layer of Ni_(68.17)Cr_(8.65)Nb_(2.98)P_(16.42)B_(3.28)Si_(0.5) metallic glass rods surface treated in a sodium dichromate solution is 4.8% (analysis of Table 12), while the Ni-ion release rate during exposure of those rods to an artificial perspiration solution is 0.62 μg/cm²/week (Table 5). The average Cr concentration in the passive layer of Ni_(68.17)Cr_(8.65)Nb_(2.98)P_(16.42)B_(3.28)Si_(0.5) metallic glass rods surface treated by a two-step chemical solution treatment is 6.2% (analysis of Table 13), while the Ni-ion release rate during exposure of those rods to an artificial perspiration solution is 0.032 μg/cm²/week (Table 5). The Ni ion release rate in units of μg/cm²/week can be denoted as y, while the average atomic concentration of Cr in the passive layer in units of atomic percent can be denoted as x. These three data points reveal that as the average atomic concentration of Cr in the passive layer increases, the Ni ion release rate decreases.

FIG. 31 presents a plot of the logarithm of the Ni ion release rate (log(y), on the vertical axis) against the average atomic concentration of Cr in the passive layer in units of atomic percent, denoted as x (on the horizontal axis). The three data points discussed above are presented by round symbols. A fit through the three data points is also presented by a solid line. The fit reveals a one-to-one correspondence between log(y) and x, suggesting a power-law correlation governed by the following equation:

log(y)=ax+b  EQ. (1)

where a=−1.0198 and b=4.8122.

In various embodiments, the Ni ion release rate in a saline solution from a Ni-based metallic glass that has been surface treated according to embodiments of the disclosure in a given solution is related to the average atomic concentration of Cr in the passive layer by a power-law according to EQ. (1), where the Ni ion release rate is in units of μg/cm²/week and the average atomic concentration of Cr is in units of atomic percent, and where a is between −0.5 and −5 and b is between 1 and 10. In other embodiments, a is between −0.25 and −2.5 and b is between 2 and 8. In yet other embodiments, a is between −0.5 and −1.5 and b is between 3 and 7.

In contrast with Nitinol, Stainless Steel, and CoCr alloys, the passivation of the Ni-based metallic glasses may not rely on the formation of a stable metal oxide such as Cr₂O₃, TiO₂, or Nb₂O₅ for example. Instead, a different mechanism involving formation of a combination of oxides and phosphides of Cr and/or Mo is present in the current alloys. Such compounds are likely to form on the surface of the Ni-based metallic glasses, which would act as Ni leach barriers.

In specific examples of Cr and P bearing Ni-based metallic glasses, such as Ni_(68.17)Cr_(8.65)Nb_(2.98)P_(16.42)B_(3.28)Si_(0.5) and Ni_(71.4)Cr_(5.52)Nb_(3.38)P_(16.67)B_(3.03) metallic glasses, formation of a passive Ni-depleted and Cr-rich and P-rich layer occurs as a consequence of the chemical surface treatment. Having higher Cr content, Ni_(71.4)Cr_(5.52)Nb_(3.38)P_(16.67)B_(3.03) likely forms a more stable chromium oxide/phosphide layer and therefore demonstrates a lower Ni-ion release rate in both treated and untreated states.

In the specific example of Mo and P bearing Cr-free Ni-based metallic glass, such as Ni_(73.0)Mo_(2.5)Nb_(3.5)Mn_(1.5)P_(18.0)Si_(1.5) metallic glass, formation of a passive Ni-depleted and Mo-rich and P-rich layer may occur as a consequence of the chemical surface treatment. The import of Cr from the chromate solution is also likely to promote the formation a chromium oxide/phosphide layer, which has been demonstrated here to mitigate Ni leaching.

In various embodiments, the passive layer of a sample of a Ni-based metallic glass that has been surface treated is thicker compared to the passive layer of an untreated sample.

In various embodiments, the average concentration of O within the passive layer of a sample of a Ni-based metallic glass that has been surface treated according to the disclosure is higher compared to an untreated sample.

In various embodiments, the average concentration of Ni within the passive layer of a sample of a Ni-based metallic glass that has been surface treated according to the disclosure is lower compared to an untreated sample.

In various embodiments, the average concentration of P within the passive layer of a sample of a Ni-based metallic glass comprising P that has been surface treated according to the disclosure is higher compared to an untreated sample.

In various embodiments, the average concentration of Cr within the passive layer of a sample of a Ni-based metallic glass comprising Cr that has been surface treated according to the disclosure is higher compared to an untreated sample.

In various embodiments, a Ni-based metallic glass that comprises at least one of Cr and Mo, the average atomic concentration of Cr and/or Mo within the passive layer is higher than the respective concentrations in the inner bulk material portion. In another embodiment, the average atomic concentration of Cr and/or Mo within the passive layer is at least 2% higher than the respective concentrations in the inner bulk material portion. In another embodiment, the average atomic concentration of Cr and/or Mo within the passive layer is at least 5% higher than the respective concentrations in the inner bulk material portion. In another embodiment, the average atomic concentration of Cr and/or Mo within the passive layer is at least 10% higher than the respective concentrations in the inner bulk material portion. In another embodiment, the average atomic concentration of Cr and/or Mo within the passive layer is at least 20% higher than the respective concentrations in the inner bulk material portion.

In various embodiments, a Ni-based metallic glass that comprises P, the average atomic concentration of P within the passive layer is higher than the P concentration in the inner bulk material portion. In another embodiment, the average atomic concentration of P within the passive layer is at least 5% higher than the P concentration in the inner bulk material portion. In another embodiment, the average atomic concentration of P within the passive layer is at least 10% higher than the P concentration in the inner bulk material portion. In another embodiment, the average atomic concentration of P within the passive layer is at least 20% higher than the P concentration in the inner bulk material portion. In another embodiment, the average atomic concentration of P within the passive layer is at least 30% higher than the P concentration in the inner bulk material portion.

Description of Methods of Producing the Alloy Ingots

The specific method used to produce the example alloy ingots involves inductive melting of the appropriate amounts of elemental constituents in a fused silica crucible under inert atmosphere. The specific purity levels of the constituent elements used to create the example alloys were as follows: Ni 99.995%, Cr 99.996%, Mo 99.95%, Mn 99.98%, Nb 99.95%, B 99.5%, P 99.9999%, and Si 99.9999%.

Description of the Method of Producing Metallic Glass Samples

Metallic glass rods of Ni_(68.17)Cr_(8.65)Nb_(2.98)P_(16.42)B_(3.28)Si_(0.5) and Ni_(71.4)Cr_(5.52)Nb_(3.38)P_(16.67)B_(3.03) 5 mm in diameter were produced from the alloy ingots using counter-gravity casting. In the counter-gravity casting process, molten liquid contained in fused silica is injected upwards (against gravity) into a mold using gas pressure. A feedstock of about 60 g was used for each rod. An inert atmosphere was created in the melt chamber by first applying vacuum at mbar and subsequently following several purges with argon, an argon atmosphere was 5×10⁻² mbar established having a pressure of −20 in-Hg. The feedstock was heated inductively first to 1350° C. and back to 1250° C. to create a homogeneous high temperature melt, and subsequently urged upwards using an argon pressure of 10 psi through a fused silica tube of 4 mm inner diameter into an H13 tool steel mold fill a rod-shaped cavity with a diameter of 5 mm and length of 100 mm. The melt was rapidly cooled in the mold to produce an amorphous rod. The amorphicity of the rods was verified by x-ray diffraction. The cast amorphous rods were sectioned into 10 mm-long segments. Both ends of the sectioned rods were polished with a 1200-grit sandpaper.

Metallic glass rods of Ni_(73.0)Mo_(2.5)Nb_(3.5)Mn_(1.5)P_(18.0) Si_(1.5) 3 mm in diameter were produced from the alloy ingots by quartz tube casting. The method for producing metallic glass rods from the alloy ingots involves re-melting the alloy ingots in quartz tubes having 0.5-mm thick walls in a furnace at 1350° C., under high purity argon and rapidly quenching in a room-temperature water bath. The cast amorphous rods were sectioned into 10 mm-long segments. Both ends of the sectioned rods were polished with a 1200-grit sandpaper.

Description of the Methods of Chemical Surface Treatment

The Ni-based amorphous rods were subjected to the following chemical surface treatments:

Immersion in a 10 weight % citric acid at room temperature for 60 min.

Immersion in a 20 volume % nitric acid at room temperature for 60 min.

Immersion in a 30 volume % nitric acid at room temperature for 60 min.

Immersion in a 40 volume % nitric acid at room temperature for 60 min.

Immersion in a 50 g/L sodium dichromate at 60° C. for 30 min.

Immersion in a 20 volume % nitric acid combined with 44 g/L sodium dichromate at 60° C. for 30 min.

Immersion in a 40 volume % nitric acid combined with 22 g/L sodium dichromate at 60° C. for 30 min.

Immersion in a two-step treatment consisting of: (1) a 20 volume % nitric acid combined with 25 g/L sodium dichromate at 60° C. for 30 min followed by water rinse, and (2) a 50 g/L sodium dichromate at 60° C. for 30 min.

Following each immersion step, the samples were thoroughly rinsed in water and dried.

Test Methodology for Ni Extraction

Ni was extracted from rods of Ni_(71.4)Cr_(5.52)Nb_(3.38)P_(16.67)B_(3.03) with a surface area of ˜1.6 cm² (4.5 mm-diameter and 10 mm-long) in a 1×PBS (Phosphate Buffered Solution) solution—a simulated body fluid solution—for 24 hours (one day), 144 hours (6 days), and 192 hours (8 days), at 37±1° C. under static condition, respectively. The solution was replaced with fresh solution for each extraction. The same sample was used for each time point. The PBS solution with a pH of 7.4 had a concentration of 8.0 g/L NaCl, 0.2 g/L KCl, 1.44 g/L Na₂HPO₄, and 0.24 g/L KH₂PO₄. Ni extraction was performed in 1.6±0.1 mL of working solutions for a total of one day, 7 days, and 15 days, at 37±1° C. under static condition. The solution volume to sample surface area ratio is ˜1 mL/cm² as recommended by ISO standards 10993 and BS EN1811:2011.

Ni was extracted from rods of Ni_(68.17)Cr_(8.65)Nb_(2.98)P_(16.42)B_(3.28)Si_(0.5) with a surface area of ˜1.6 cm² (4.5 mm-diameter and 10 mm-long) in a Fusayama/Mayer Artificial Saliva solution for 24 hours (one day), 144 hours (6 days), and 192 hours (8 days), at 37±1° C. under static condition, respectively. The solution was replaced with fresh solution for each extraction. The same sample was used for each time point. The Fusayama/Mayer Artificial Saliva solution with a pH of 4.9 had a concentration of 0.4 g/L NaCl, 0.4 g/L KCl, 0.795 g/L CaCl₂-2H₂O, 0.690 g/L NaH₂PO₄—H₂O, 0.005 g/L Na₂S.9H₂O, and 1 g/L Urea. Ni extraction was performed in 1.6±0.1 mL of working solutions for a total of one day, 7 days, and 15 days, at 37±1° C. under static condition. The solution volume to sample surface area ratio is ˜1 mL/cm² as recommended by ISO standards 10993 and BS EN1811:2011.

Ni was extracted from rods of Ni_(68.17)Cr_(8.65)Nb_(2.98)P_(16.42)B_(3.28)Si_(0.5) with a surface area of ˜1.6 cm² (4.5 mm-diameter and 10 mm-long) in an artificial perspiration solution. The pH of the solution was adjusted to 6.5±0.05 prior to sample immersion. The artificial perspiration solution was prepared according to guidelines from BS EN1811:2011, and has a concentration of 0.5% sodium chloride, 0.1% lactic acid, and 0.1% urea. Sodium hydroxide was added to adjust the pH, according to guidelines from BS EN1811:2011. Ni extraction was performed in 1.6±0.1 mL of working solutions for a total of 7 days at 30±2° C. under static condition. The solution volume to sample surface area ratio is ˜1 mL/cm² as recommended by ISO standards 10993 and BS EN1811:2011.

Ni was extracted from rods of Ni_(73.0)Mo_(2.5)Nb_(3.5)Mn_(1.5)P_(18.0)Si_(1.5) with a surface area of 1.0 cm² (2.8 mm-diameter and 10 mm-long) in an artificial perspiration solution. The pH of the solution was adjusted to 6.5±0.05 prior to sample immersion. The artificial perspiration solution was prepared according to guidelines from BS EN1811:2011, and has a concentration of 0.5% sodium chloride, 0.1% lactic acid, and 0.1% urea. Sodium hydroxide was added to adjust the pH, according to guidelines from BS EN1811:2011. Ni extraction was performed in 1.0±0.1 mL of working solutions for a total of 7 days at 30±2° C. under static condition. The solution volume to sample surface area ratio is ˜1 mL/cm² as recommended by ISO standards 10993 and BS EN1811:2011.

Test Methodology for Assessing the Ni-Ion Release Rate

The Ni concentration in the PBS and Fusayama/Mayer Artificial Saliva extraction solutions was analyzed by ICP-MS/AES for 24 hours (one day), 144 hours (6 days), and 192 hours (8 days) of immersion. The Ni in the artificial perspiration solution was analyzed by ICP-MS/AES for 7 days of immersion. The ICP-MS/AES instruments were calibrated with NIST traceable calibration standards. To provide a baseline, blank samples containing only PBS, only Fusayama/Mayer Artificial Saliva, and only artificial perspiration solutions were also extracted.

For each time point, the Ni concentrations were calculated using the formula:

Ni concentration (in ppb)=(C _(s) −C _(b))×(W _(f) /W _(i)),

where C_(s) is the measured concentration (ppb) in the prepared sample solution, C_(b) is the measured concentration (ppb) in the prepared blank solution, W_(f) is the final weight of the prepared sample (g), and W, is the initial weight of the prepared sample (g). The Ni release in ng/cm² was then calculated by multiplying the Ni concentration (in ppb) by the solution volume (in mL) and dividing by the surface area of the sample (in cm²), as follows:

${{Ni}\mspace{14mu} {release}\mspace{14mu} \left( {{in}\mspace{14mu} {{ng}/{cm}^{2}}} \right)} = {\frac{{Ni}\mspace{14mu} {concentration}\mspace{14mu} \left( {{in}\mspace{14mu} {ppb}} \right) \times {solution}\mspace{14mu} {volume}\mspace{14mu} \left( {{in}\mspace{14mu} {mL}} \right)}{{sample}\mspace{14mu} {surface}\mspace{14mu} {area}\mspace{14mu} \left( {{in}\mspace{14mu} {cm}^{2}} \right)}.}$

In the formula above it is assumed that 1 ppb=1 ng/mL, which is valid for an aqueous solution. Per the formula above, the weekly Ni release in artificial perspiration extraction solution at the end of the extraction periods of 7 days was recorded. Also, the Ni release in PBS and Fusayama/Mayer Artificial Saliva extraction solutions at the end of the extraction periods of 1, 6 and 8 days, corresponding to total immersion periods of 1, 7, and 15 days, was recorded.

In calculating daily Ni release rates in PBS and Fusayama/Mayer Artificial Saliva extraction solutions, the average daily Ni release rate over each extraction period was then calculated by dividing the Ni release recorded over the extraction period by the number of days of extraction, and is listed in Tables 1 and 3. In one example, the first extraction period was one day, which represents a total immersion period of one day. The Ni release recorded at the end of the first extraction period was divided by the extraction period of one day to give the average daily Ni release rate over the immersion period of one day, which is listed in Tables 1 and 3. In another example, the second extraction period was 6 days, which represents a total immersion period of 7 days. The Ni release recorded at the end of the second extraction period was divided by the extraction period of 6 days to give the average daily Ni release rate over the immersion period of 2-7 days, which is listed in Tables 1 and 3. In yet another example, the third extraction period was 8 days, which represents a total immersion period of 15 days. The Ni release recorded at the end of the third extraction period was divided by the extraction period of 8 days to give the average daily Ni release rate over the immersion period of 8-15 days, which is listed in Tables 1 and 3.

In calculating weekly Ni release rates from daily Ni release rates in PBS and Fusayama/Mayer Artificial Saliva extraction solutions, the weekly Ni release rate for the first week of immersion, listed in Tables 2 and 4, was calculated by adding the Ni release recorded at the end of the first extraction period of one day, and the Ni release recorded at the end of the second extraction period of 6 days. The weekly Ni release rate for the second week of immersion, listed in Tables 2 and 4, was calculated by adding the Ni release recorded at the end of the second extraction period of 8 days.

Test Methodology for Assessing the Surface and in-Depth Chemical Composition

The surface and in-depth chemical composition analysis was performed by X-ray photoelectron spectroscopy (XPS) and electron spectroscopy for chemical analysis (ESCA) on the cross-section area of as-polished and surface treated Ni_(68.17)Cr_(8.65)Nb_(2.98)P_(16.42)B_(3.28)Si_(0.5) metallic glass rod samples. XPS data is quantified using relative sensitivity factors and a model that assumes a homogeneous layer. The analysis volume is the product of the analysis area (spot size or aperture size) and the depth of information. Photoelectrons are generated within the X-ray penetration depth (typically many microns), but only the photoelectrons within the top three photoelectron escape depths are detected. Escape depths are on the order of 15-35 Å, which leads to an analysis depth of ˜50-100 Å. Typically, 95% of the signal originates from within this depth. Depth profiles were obtained by alternating an acquisition cycle with a sputter cycle during which material was removed from the sample using an Ar⁺ source. The sputter rate was 50 Å/min relative to the SiO₂ standard. The analysis area was 1400 μm×300 μm. The concentrations of the elements detected by XPS are provided in atomic %. Concentration values provided are normalized to 100% using the elements detected. The atomic concentrations provided can be reproduced for major constituents of sample surfaces to better than ±10%. For elements present at levels below 10 at % down to the detection limit (at ˜0.05-0.5 at %; actual detection limit is element and spectral dependent) the uncertainty in the reproducibility of the results can be significantly larger. For elements present at levels below 10 at %, XPS should be considered a “semi-quantitative” analysis technique. Major factors affecting detection limits are the element itself (heavier elements generally have lower detection limits), interferences (can include photoelectron peaks and Auger electron peaks from other elements) and background (mainly caused by signal from electrons that have lost energy to the matrix).

The surface and in-depth chemical composition analysis was also performed by Secondary Ion Mass Spectrometry (SIMS) on the cross-section area of as-polished and surface treated Ni_(68.17)Cr_(8.65)Nb_(2.98)P_(16.42)B_(3.28)Si_(0.5) metallic glass rod samples. SIMS provides elemental depth profiles over a depth range of few angstrom (Å) to tens of microns. The samples are sputtered/etched with a beam of primary ions (usually O or Cs). Secondary ions formed during the sputtering process are extracted and analyzed using a mass spectrometer. The secondary ions can range in concentration from matrix levels down to sub-ppm trace levels. SIMS provides ultra-high depth resolution profiling with detection limit and depth resolution better than 10¹⁰-10¹⁶ at/cm³ and 5 Å, respectively. Chemical composition analysis of the samples was performed every 1-1.5 Å in depth. SIMS allows detection of all elements and isotopes, including B and Si. The lateral resolution/probe size is 10 μm or better. The concentrations of the elements detected by SIMS are provided in atomic %. SIMS is element specific, and in the context of the present disclosure it was performed for detection of O, P, Cr, Nb, B, Si, and Ni, while elements that contribute to the organic layer, such as C, N, and H, were not detected. Because the detected concentrations are element specific, i.e., not normalized to 100% using the elements detected, summation of the concentrations does not necessarily add up to 100%. The atomic concentrations provided can be reproduced for major constituents of sample surfaces. 

What is claimed is:
 1. A method of treating the surface of a Ni-based metallic glass comprising: immersing at least a portion of the Ni-based metallic glass in a chemical treatment solution comprising at least one of an acid solution, a chromate solution, or a molybdate solution to produce a surface treated portion; and removing the surface treated portion from the chemical treatment solution; wherein the Ni ion release rate from the surface treated portion when immersed in a saline solution for one day is less than 80% of the Ni ion release rate from an as-cast Ni-based metallic glass having the same composition and having been immersed in the saline solution for one day.
 2. The method of treating the surface of a Ni-based metallic glass of claim 1, wherein a duration of immersing in the chemical treatment solution is at least 1 minute.
 3. The method of treating the surface of a Ni-based metallic glass of claim 1, wherein the temperature of the chemical treatment solution ranges between 10° C. and 80° C.
 4. The method of treating the surface of a Ni-based metallic glass of claim 1, wherein the chemical treatment solution is a nitric acid solution, and where the nitric acid concentration is between 5 and 60 volume %.
 5. The method of treating the surface of a Ni-based metallic glass of claim 1, wherein the chemical treatment solution is a sodium dichromate solution, and where the sodium dichromate concentration is between 5 and 200 g/L.
 6. The method of treating the surface of a Ni-based metallic glass of claim 1, wherein the chemical treatment solution is a disodium molybdate solution, and where the disodium molybdate concentration is between 10 and 100 g/L.
 7. The method of treating the surface of a Ni-based metallic glass of claim 1, where the saline solution has a pH of at least
 2. 8. The method of treating the surface of a Ni-based metallic glass of claim 1, where the saline solution has a concentration of NaCl of at least 0.1 g/L.
 9. The method of treating the surface of a Ni-based metallic glass of claim 1, where the saline solution is selected from artificial saliva and artificial perspiration.
 10. The method of treating the surface of a Ni-based metallic glass of claim 9, wherein the Ni ion release rate from the treated portion of the Ni-based metallic glass when immersed in artificial perspiration is less than 0.88 μg/cm²/week.
 11. The method of treating the surface of a Ni-based metallic glass of claim 1, wherein a mass of Ni ion released from the treated portion of the Ni-based metallic glass when immersed in artificial saliva for one day is less than 35 μg.
 12. A method of treating the surface of a Ni-based metallic glass comprising: immersing at least a portion of the Ni-based metallic glass in an acidic first chemical treatment solution; removing the portion from the acidic first chemical treatment solution; immersing the portion in a second chemical treatment solution comprising at least one of a chromate solution or a molybdenum solution; and removing the portion from the second chemical treatment solution to produce a surface treated portion; wherein the Ni ion release rate from the surface treated portion when immersed in a saline solution for one day is less than 80% of the Ni ion release rate from an as-cast Ni-based metallic glass having the same composition and having been immersed in the saline solution for one day.
 13. The method of treating the surface of a Ni-based metallic glass of claim 12, wherein the acidic first chemical treatment solution comprises a nitric acid solution having a concentration between 5 and 60 volume %.
 14. The method of treating the surface of a Ni-based metallic glass of claim 12, wherein the second chemical treatment solution comprises a sodium dichromate solution at concentration between 5 and 200 g/L.
 15. The method of treating the surface of a Ni-based metallic glass of claim 12, wherein the second chemical treatment solution comprises a disodium molybdate solution at a concentration between 10 and 100 g/L.
 16. A passivated Ni-based metallic glass comprising: an inner bulk material portion, and an outer passive layer portion having an average combined atomic concentration of Cr and Mo greater than the average combined atomic concentration of Cr and Mo in the inner bulk material portion.
 17. The passivated Ni-based metallic glass of claim 16, wherein the outer passive layer is amorphous.
 18. The passivated Ni-based metallic glass of claim 16, wherein the composition of the Ni-based metallic glass is defined by the formula: Ni_(100-a-b)X_(a)Z_(b) wherein: X is Cr, Mo, Mn, Nb, Ta, Fe, Co, Cu or combinations thereof; Z is P, B, Si, or combinations thereof; a is between 5 and 25; and b is between 15 and
 25. 19. The passivated Ni-based metallic glass of claim 16, wherein the average atomic concentration of Cr and Mo in the outer passive layer is at least 2% higher than the average atomic concentration of Cr and Mo in the inner bulk material portion.
 20. The passivated Ni-based metallic glass of claim 16, wherein the average atomic concentration of P in the outer passive layer is at least 5% higher than the average atomic concentration of P in the inner bulk material portion. 